diff --git a/lib/completely/pattern.rb b/lib/completely/pattern.rb
index a276a29..1c6f6b7 100644
--- a/lib/completely/pattern.rb
+++ b/lib/completely/pattern.rb
@@ -54,8 +54,16 @@ def compgen
     def compgen!
       result = []
       result << actions.join(' ').to_s if actions.any?
-      result << %[-W "$(#{function_name} "#{words.join ' '}")"] if words.any?
+      result << %[-W "$(#{function_name} #{quoted_words.join ' '})"] if words.any?
       result.any? ? result.join(' ') : nil
     end
+
+    def quoted_words
+      @quoted_words ||= words.map { |word| %("#{escape_for_double_quotes word}") }
+    end
+
+    def escape_for_double_quotes(word)
+      word.gsub(/["\\]/, '\\\\\&')
+    end
   end
 end
diff --git a/lib/completely/templates/template.erb b/lib/completely/templates/template.erb
index b5dfbe4..8b46f92 100644
--- a/lib/completely/templates/template.erb
+++ b/lib/completely/templates/template.erb
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 <%= function_name %>_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 <%= function_name %>() {
diff --git a/spec/approvals/cli/generated-script b/spec/approvals/cli/generated-script
index 94e256e..8e7ee14 100644
--- a/spec/approvals/cli/generated-script
+++ b/spec/approvals/cli/generated-script
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _mygit_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _mygit_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _mygit_completions() {
@@ -59,7 +58,7 @@ _mygit_completions() {
       ;;
 
     'status'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help --verbose --branch -b")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help" "--verbose" "--branch" "-b")" -- "$cur")
       ;;
 
     'init'*)
@@ -67,7 +66,7 @@ _mygit_completions() {
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h -v --help --version init status")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h" "-v" "--help" "--version" "init" "status")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/cli/generated-script-alt b/spec/approvals/cli/generated-script-alt
index 217aae4..23eb09b 100644
--- a/spec/approvals/cli/generated-script-alt
+++ b/spec/approvals/cli/generated-script-alt
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _mycomps_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _mycomps_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _mycomps() {
@@ -59,7 +58,7 @@ _mycomps() {
       ;;
 
     'status'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mycomps_filter "--help --verbose --branch -b")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mycomps_filter "--help" "--verbose" "--branch" "-b")" -- "$cur")
       ;;
 
     'init'*)
@@ -67,7 +66,7 @@ _mycomps() {
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mycomps_filter "-h -v --help --version init status")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mycomps_filter "-h" "-v" "--help" "--version" "init" "status")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/cli/generated-wrapped-script b/spec/approvals/cli/generated-wrapped-script
index e37ade0..875142e 100644
--- a/spec/approvals/cli/generated-wrapped-script
+++ b/spec/approvals/cli/generated-wrapped-script
@@ -6,9 +6,10 @@ give_comps() {
   echo $'# Modifying it manually is not recommended'
   echo $''
   echo $'_mygit_completions_filter() {'
-  echo $'  local words="$1"'
+  echo $'  local words=("$@")'
   echo $'  local cur=${COMP_WORDS[COMP_CWORD]}'
   echo $'  local result=()'
+  echo $'  local want_options=0'
   echo $''
   echo $'  # words the user already typed (excluding the command itself)'
   echo $'  local used=()'
@@ -16,28 +17,26 @@ give_comps() {
   echo $'    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")'
   echo $'  fi'
   echo $''
-  echo $'  if [[ "${cur:0:1}" == "-" ]]; then'
-  echo $'    # Completing an option: offer everything (including options)'
-  echo $'    echo "$words"'
-  echo $''
-  echo $'  else'
-  echo $'    # Completing a non-option: offer only non-options,'
-  echo $'    # and don\'t re-offer ones already used earlier in the line.'
-  echo $'    for word in $words; do'
+  echo $'  # Completing an option: offer everything.'
+  echo $'  # Completing a non-option: drop options and already-used words.'
+  echo $'  [[ "${cur:0:1}" == "-" ]] && want_options=1'
+  echo $'  for word in "${words[@]}"; do'
+  echo $'    if ((!want_options)); then'
   echo $'      [[ "${word:0:1}" == "-" ]] && continue'
   echo $''
-  echo $'      local seen=0'
   echo $'      for u in "${used[@]}"; do'
   echo $'        if [[ "$u" == "$word" ]]; then'
-  echo $'          seen=1'
-  echo $'          break'
+  echo $'          continue 2'
   echo $'        fi'
   echo $'      done'
-  echo $'      ((!seen)) && result+=("$word")'
-  echo $'    done'
+  echo $'    fi'
   echo $''
-  echo $'    echo "${result[*]}"'
-  echo $'  fi'
+  echo $'    # compgen -W expects shell-escaped words in one space-delimited string.'
+  echo $'    printf -v word \'%q\' "$word"'
+  echo $'    result+=("$word")'
+  echo $'  done'
+  echo $''
+  echo $'  echo "${result[*]}"'
   echo $'}'
   echo $''
   echo $'_mygit_completions() {'
@@ -60,7 +59,7 @@ give_comps() {
   echo $'      ;;'
   echo $''
   echo $'    \'status\'*)'
-  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help --verbose --branch -b")" -- "$cur")'
+  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help" "--verbose" "--branch" "-b")" -- "$cur")'
   echo $'      ;;'
   echo $''
   echo $'    \'init\'*)'
@@ -68,7 +67,7 @@ give_comps() {
   echo $'      ;;'
   echo $''
   echo $'    *)'
-  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h -v --help --version init status")" -- "$cur")'
+  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h" "-v" "--help" "--version" "init" "status")" -- "$cur")'
   echo $'      ;;'
   echo $''
   echo $'  esac'
diff --git a/spec/approvals/cli/test/completely-tester-1.sh b/spec/approvals/cli/test/completely-tester-1.sh
index 50d5b48..7d141a9 100644
--- a/spec/approvals/cli/test/completely-tester-1.sh
+++ b/spec/approvals/cli/test/completely-tester-1.sh
@@ -13,9 +13,10 @@ fi
 # Modifying it manually is not recommended
 
 _mygit_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -23,28 +24,26 @@ _mygit_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _mygit_completions() {
@@ -67,7 +66,7 @@ _mygit_completions() {
       ;;
 
     'status'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help --verbose --branch -b")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help" "--verbose" "--branch" "-b")" -- "$cur")
       ;;
 
     'init'*)
@@ -75,7 +74,7 @@ _mygit_completions() {
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h -v --help --version init status")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h" "-v" "--help" "--version" "init" "status")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/cli/test/completely-tester-2.sh b/spec/approvals/cli/test/completely-tester-2.sh
index a0fb1e3..73555b9 100644
--- a/spec/approvals/cli/test/completely-tester-2.sh
+++ b/spec/approvals/cli/test/completely-tester-2.sh
@@ -13,9 +13,10 @@ fi
 # Modifying it manually is not recommended
 
 _mygit_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -23,28 +24,26 @@ _mygit_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _mygit_completions() {
@@ -67,7 +66,7 @@ _mygit_completions() {
       ;;
 
     'status'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help --verbose --branch -b")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help" "--verbose" "--branch" "-b")" -- "$cur")
       ;;
 
     'init'*)
@@ -75,7 +74,7 @@ _mygit_completions() {
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h -v --help --version init status")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h" "-v" "--help" "--version" "init" "status")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/cli/test/completely-tester.sh b/spec/approvals/cli/test/completely-tester.sh
index 108dbf9..a3235d5 100644
--- a/spec/approvals/cli/test/completely-tester.sh
+++ b/spec/approvals/cli/test/completely-tester.sh
@@ -13,9 +13,10 @@ fi
 # Modifying it manually is not recommended
 
 _mygit_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -23,28 +24,26 @@ _mygit_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _mygit_completions() {
@@ -67,7 +66,7 @@ _mygit_completions() {
       ;;
 
     'status'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help --verbose --branch -b")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "--help" "--verbose" "--branch" "-b")" -- "$cur")
       ;;
 
     'init'*)
@@ -75,7 +74,7 @@ _mygit_completions() {
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h -v --help --version init status")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "-h" "-v" "--help" "--version" "init" "status")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/completions/function b/spec/approvals/completions/function
index 1b31b34..ffaa11c 100644
--- a/spec/approvals/completions/function
+++ b/spec/approvals/completions/function
@@ -6,9 +6,10 @@ send_completions() {
   echo $'# Modifying it manually is not recommended'
   echo $''
   echo $'_completely_completions_filter() {'
-  echo $'  local words="$1"'
+  echo $'  local words=("$@")'
   echo $'  local cur=${COMP_WORDS[COMP_CWORD]}'
   echo $'  local result=()'
+  echo $'  local want_options=0'
   echo $''
   echo $'  # words the user already typed (excluding the command itself)'
   echo $'  local used=()'
@@ -16,28 +17,26 @@ send_completions() {
   echo $'    used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")'
   echo $'  fi'
   echo $''
-  echo $'  if [[ "${cur:0:1}" == "-" ]]; then'
-  echo $'    # Completing an option: offer everything (including options)'
-  echo $'    echo "$words"'
-  echo $''
-  echo $'  else'
-  echo $'    # Completing a non-option: offer only non-options,'
-  echo $'    # and don\'t re-offer ones already used earlier in the line.'
-  echo $'    for word in $words; do'
+  echo $'  # Completing an option: offer everything.'
+  echo $'  # Completing a non-option: drop options and already-used words.'
+  echo $'  [[ "${cur:0:1}" == "-" ]] && want_options=1'
+  echo $'  for word in "${words[@]}"; do'
+  echo $'    if ((!want_options)); then'
   echo $'      [[ "${word:0:1}" == "-" ]] && continue'
   echo $''
-  echo $'      local seen=0'
   echo $'      for u in "${used[@]}"; do'
   echo $'        if [[ "$u" == "$word" ]]; then'
-  echo $'          seen=1'
-  echo $'          break'
+  echo $'          continue 2'
   echo $'        fi'
   echo $'      done'
-  echo $'      ((!seen)) && result+=("$word")'
-  echo $'    done'
+  echo $'    fi'
   echo $''
-  echo $'    echo "${result[*]}"'
-  echo $'  fi'
+  echo $'    # compgen -W expects shell-escaped words in one space-delimited string.'
+  echo $'    printf -v word \'%q\' "$word"'
+  echo $'    result+=("$word")'
+  echo $'  done'
+  echo $''
+  echo $'  echo "${result[*]}"'
   echo $'}'
   echo $''
   echo $'_completely_completions() {'
@@ -52,7 +51,7 @@ send_completions() {
   echo $''
   echo $'  case "$compline" in'
   echo $'    \'generate\'*)'
-  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help --force")" -- "$cur")'
+  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help" "--force")" -- "$cur")'
   echo $'      ;;'
   echo $''
   echo $'    \'init\'*)'
@@ -60,7 +59,7 @@ send_completions() {
   echo $'      ;;'
   echo $''
   echo $'    *)'
-  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_completely_completions_filter "--help --version init generate")" -- "$cur")'
+  echo $'      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_completely_completions_filter "--help" "--version" "init" "generate")" -- "$cur")'
   echo $'      ;;'
   echo $''
   echo $'  esac'
diff --git a/spec/approvals/completions/script b/spec/approvals/completions/script
index cba794b..bb33f7b 100644
--- a/spec/approvals/completions/script
+++ b/spec/approvals/completions/script
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _completely_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _completely_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _completely_completions() {
@@ -51,7 +50,7 @@ _completely_completions() {
 
   case "$compline" in
     'generate'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help --force")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help" "--force")" -- "$cur")
       ;;
 
     'init'*)
@@ -59,7 +58,7 @@ _completely_completions() {
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_completely_completions_filter "--help --version init generate")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_completely_completions_filter "--help" "--version" "init" "generate")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/completions/script-complete-options b/spec/approvals/completions/script-complete-options
index a0dff27..8e6347c 100644
--- a/spec/approvals/completions/script-complete-options
+++ b/spec/approvals/completions/script-complete-options
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _mygit_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _mygit_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _mygit_completions() {
@@ -51,7 +50,7 @@ _mygit_completions() {
 
   case "$compline" in
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "status commit")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_mygit_completions_filter "status" "commit")" -- "$cur")
       ;;
 
   esac
diff --git a/spec/approvals/completions/script-only-spaces b/spec/approvals/completions/script-only-spaces
index 44695a6..f980115 100644
--- a/spec/approvals/completions/script-only-spaces
+++ b/spec/approvals/completions/script-only-spaces
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _completely_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _completely_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _completely_completions() {
@@ -51,7 +50,7 @@ _completely_completions() {
 
   case "$compline" in
     'generate'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help --force")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -A directory -W "$(_completely_completions_filter "--help" "--force")" -- "$cur")
       ;;
 
     'init'*)
diff --git a/spec/approvals/completions/script-with-debug b/spec/approvals/completions/script-with-debug
index afc0053..7a3673c 100644
--- a/spec/approvals/completions/script-with-debug
+++ b/spec/approvals/completions/script-with-debug
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _completely_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _completely_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _completely_completions() {
diff --git a/spec/completely/pattern_spec.rb b/spec/completely/pattern_spec.rb
index 912ed3e..93952a4 100644
--- a/spec/completely/pattern_spec.rb
+++ b/spec/completely/pattern_spec.rb
@@ -105,7 +105,7 @@
 
   describe '#compgen' do
     it 'returns a line of compgen arguments' do
-      expect(subject.compgen).to eq '-A file -A user -W "$(_filter "--message --help")"'
+      expect(subject.compgen).to eq '-A file -A user -W "$(_filter "--message" "--help")"'
     end
 
     context 'when there are no words for -W' do
@@ -120,7 +120,15 @@
       let(:completions) { %w[--message --help] }
 
       it 'omits the -A arguments' do
-        expect(subject.compgen).to eq '-W "$(_filter "--message --help")"'
+        expect(subject.compgen).to eq '-W "$(_filter "--message" "--help")"'
+      end
+    end
+
+    context 'when words include spaces and quotes' do
+      let(:completions) { ['hello world', 'one"quote'] }
+
+      it 'shell-escapes words before passing them to the filter' do
+        expect(subject.compgen).to eq '-W "$(_filter "hello world" "one\"quote")"'
       end
     end
 
diff --git a/spec/fixtures/tester/default.bash b/spec/fixtures/tester/default.bash
index a5a878f..c4df327 100644
--- a/spec/fixtures/tester/default.bash
+++ b/spec/fixtures/tester/default.bash
@@ -5,9 +5,10 @@
 # Modifying it manually is not recommended
 
 _cli_completions_filter() {
-  local words="$1"
+  local words=("$@")
   local cur=${COMP_WORDS[COMP_CWORD]}
   local result=()
+  local want_options=0
 
   # words the user already typed (excluding the command itself)
   local used=()
@@ -15,28 +16,26 @@ _cli_completions_filter() {
     used=("${COMP_WORDS[@]:1:$((COMP_CWORD - 1))}")
   fi
 
-  if [[ "${cur:0:1}" == "-" ]]; then
-    # Completing an option: offer everything (including options)
-    echo "$words"
-
-  else
-    # Completing a non-option: offer only non-options,
-    # and don't re-offer ones already used earlier in the line.
-    for word in $words; do
+  # Completing an option: offer everything.
+  # Completing a non-option: drop options and already-used words.
+  [[ "${cur:0:1}" == "-" ]] && want_options=1
+  for word in "${words[@]}"; do
+    if ((!want_options)); then
       [[ "${word:0:1}" == "-" ]] && continue
 
-      local seen=0
       for u in "${used[@]}"; do
         if [[ "$u" == "$word" ]]; then
-          seen=1
-          break
+          continue 2
         fi
       done
-      ((!seen)) && result+=("$word")
-    done
+    fi
 
-    echo "${result[*]}"
-  fi
+    # compgen -W expects shell-escaped words in one space-delimited string.
+    printf -v word '%q' "$word"
+    result+=("$word")
+  done
+
+  echo "${result[*]}"
 }
 
 _cli_completions() {
@@ -51,19 +50,19 @@ _cli_completions() {
 
   case "$compline" in
     'command childcommand'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--quiet --verbose -q -v")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--quiet" "--verbose" "-q" "-v")" -- "$cur")
       ;;
 
     'command subcommand'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--force --quiet")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--force" "--quiet")" -- "$cur")
       ;;
 
     'command'*)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "subcommand childcommand")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "subcommand" "childcommand")" -- "$cur")
       ;;
 
     *)
-      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--help --version command conquer")" -- "$cur")
+      while read -r; do COMPREPLY+=("$REPLY"); done < <(compgen -W "$(_cli_completions_filter "--help" "--version" "command" "conquer")" -- "$cur")
       ;;
 
   esac