diff --git a/pkgs/development/python-modules/pyadjoint-ad/default.nix b/pkgs/development/python-modules/pyadjoint-ad/default.nix
index c3417350b646..c20a2787f2f8 100644
--- a/pkgs/development/python-modules/pyadjoint-ad/default.nix
+++ b/pkgs/development/python-modules/pyadjoint-ad/default.nix
@@ -4,6 +4,7 @@
   fetchFromGitHub,
   setuptools,
   scipy,
+  sympy,
   checkpoint-schedules,
   pytestCheckHook,
 }:
@@ -26,6 +27,7 @@ buildPythonPackage (finalAttrs: {
 
   dependencies = [
     scipy
+    sympy
     checkpoint-schedules
   ];