diff --git a/CITATION.cff b/CITATION.cff
index a2b386b6..aeef8457 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -41,5 +41,5 @@ abstract: >-
   A Python package that wraps the functionality of the C++
   library libsemigroups.
 license: GPL-3.0+
-version: 1.3.0
-date-released: "2026-01-18"
+version: 1.4.0
+date-released: "2026-02-25"
diff --git a/README.md b/README.md
index b10425f7..bff1f957 100644
--- a/README.md
+++ b/README.md
@@ -150,10 +150,10 @@ uv pip install .
 To build `libsemigroups_pybind11` from a release archive:
 
 ```console
-curl -L -O https://github.com/libsemigroups/libsemigroups_pybind11/releases/latest/download/libsemigroups_pybind11-1.3.0.tar.gz
-tar -xf libsemigroups_pybind11-1.3.0.tar.gz
-rm -f libsemigroups_pybind11-1.3.0.tar.gz
-cd libsemigroups_pybind11-1.3.0
+curl -L -O https://github.com/libsemigroups/libsemigroups_pybind11/releases/latest/download/libsemigroups_pybind11-1.4.0.tar.gz
+tar -xf libsemigroups_pybind11-1.4.0.tar.gz
+rm -f libsemigroups_pybind11-1.4.0.tar.gz
+cd libsemigroups_pybind11-1.4.0
 pip install .
 ```
 
diff --git a/build_tools/__init__.py b/build_tools/__init__.py
index ae8f9a7f..f5a48a3a 100644
--- a/build_tools/__init__.py
+++ b/build_tools/__init__.py
@@ -11,4 +11,4 @@ def minimum_libsemigroups_version():
     """Returns the minimum required version of libsemigroups required to build
     libsemigroups_pybind11.
     """
-    return "3.4.0"
+    return "3.5.1"
diff --git a/docs/source/changelog-v1.rst b/docs/source/changelog-v1.rst
index d3413c86..cdd933e6 100644
--- a/docs/source/changelog-v1.rst
+++ b/docs/source/changelog-v1.rst
@@ -1,5 +1,5 @@
 ..
-    Copyright (c) 2025, J. D. Mitchell
+    Copyright (c) 2025-2026, J. D. Mitchell
 
     Distributed under the terms of the GPL license version 3.
 
@@ -8,6 +8,16 @@
 Changelog - version 1
 =====================
 
+v1.4.0 (released 25/02/2026)
+----------------------------
+
+This is a minor release including some improvements and new features:
+
+* Update to libsemigroups v3.5.0 and add the new features it contains.
+* transf: future proof ``__getitem__`` by @james-d-mitchell in https://github.com/libsemigroups/libsemigroups_pybind11/pull/382
+* todd-coxeter: update for changes in libsemigroups by @james-d-mitchell in https://github.com/libsemigroups/libsemigroups_pybind11/pull/388
+
+
 v1.3.0 (released 18/01/2026)
 ----------------------------
 
diff --git a/docs/source/install.rst b/docs/source/install.rst
index f821d150..7937f6e0 100644
--- a/docs/source/install.rst
+++ b/docs/source/install.rst
@@ -101,10 +101,10 @@ To build ``libsemigroups_pybind11`` from a release archive:
 
 ::
 
-    $ curl -L -O https://github.com/libsemigroups/libsemigroups_pybind11/releases/latest/download/libsemigroups_pybind11-1.3.0.tar.gz
-    $ tar -xf libsemigroups_pybind11-1.3.0.tar.gz
-    $ rm -f libsemigroups_pybind11-1.3.0.tar.gz
-    $ cd libsemigroups_pybind11-1.3.0
+    $ curl -L -O https://github.com/libsemigroups/libsemigroups_pybind11/releases/latest/download/libsemigroups_pybind11-1.4.0.tar.gz
+    $ tar -xf libsemigroups_pybind11-1.4.0.tar.gz
+    $ rm -f libsemigroups_pybind11-1.4.0.tar.gz
+    $ cd libsemigroups_pybind11-1.4.0
     $ pip install .
 
 Building the documentation
diff --git a/src/transf.cpp b/src/transf.cpp
index 69920a0f..9e5126e0 100644
--- a/src/transf.cpp
+++ b/src/transf.cpp
@@ -733,7 +733,7 @@ fewer points requiring less space per point.
       m.def("transf_inverse",
             py::overload_cast<Perm_ const&>(&inverse<N, Scalar>));
     }  // bind_perm
-  }  // namespace
+  }    // namespace
 
   void init_transf(py::module& m) {
     // Transformations