diff --git a/master/custom/builders.py b/master/custom/builders.py
index 9a7a4a67..57054718 100644
--- a/master/custom/builders.py
+++ b/master/custom/builders.py
@@ -1,6 +1,7 @@
 from custom.factories import (
     UnixBuild,
     UnixPerfBuild,
+    UnixXPickleBuild,
     RHEL8Build,
     CentOS9Build,
     FedoraStableBuild,
@@ -208,6 +209,9 @@
     # Ubuntu Linux AArch64
     ("aarch64 Ubuntu 24.04 BigMem", "diegorusso-aarch64-bigmem", UnixBigmemBuild),
 
+    # test_xpickle
+    ("aarch64 Ubuntu test_xpickle", "stan-aarch64-ubuntu", UnixXPickleBuild),
+
     # Linux x86-64 GCC
     # Fedora Rawhide is unstable
     ("AMD64 Fedora Rawhide", "cstratak-fedora-rawhide-x86_64", FedoraRawhideBuild),
diff --git a/master/custom/factories.py b/master/custom/factories.py
index f7e54eec..f82c6ff2 100644
--- a/master/custom/factories.py
+++ b/master/custom/factories.py
@@ -290,6 +290,12 @@ class UnixBigmemBuild(UnixBuild):
     factory_tags = ["bigmem"]
 
 
+class UnixXPickleBuild(UnixBuild):
+    buildersuffix = ".xpickle"
+    testFlags = ["-uxpickle", "test_xpickle"]
+    factory_tags = ["xpickle"]
+
+
 class NonDebugUnixBuild(UnixBuild):
     buildersuffix = ".nondebug"
     # Enable assertions regardless. Some children will override this,
diff --git a/master/custom/workers.py b/master/custom/workers.py
index 8f0e1a89..4148ea90 100644
--- a/master/custom/workers.py
+++ b/master/custom/workers.py
@@ -184,6 +184,13 @@ def get_workers(settings):
                   'aarch32', 'arm'],
             parallel_tests=4,
         ),
+        cpw(
+            name="stan-aarch64-ubuntu",
+            tags=['linux', 'unix', 'ubuntu', 'arm', 'arm64', 'aarch64'],
+            parallel_tests=4,
+            # test_xpickle doesn't exist on these branches
+            not_branches=['3.12', '3.11', '3.10'],
+        ),
         cpw(
             name="stan-raspbian",
             tags=['linux', 'unix', 'raspbian', 'debian', 'armv8',