diff --git a/pkgs/by-name/ti/tiddit/package.nix b/pkgs/by-name/ti/tiddit/package.nix
index 18dd004dd0c8..97851f95bd49 100644
--- a/pkgs/by-name/ti/tiddit/package.nix
+++ b/pkgs/by-name/ti/tiddit/package.nix
@@ -38,6 +38,7 @@ python3Packages.buildPythonApplication rec {
         ropebwt2
       ]
     }"
+    "--set PYTHONPATH $PYTHONPATH"
   ];
 
   meta = {