diff --git a/pkgs/development/python-modules/onnx/default.nix b/pkgs/development/python-modules/onnx/default.nix
index 807b6cf5f5e107..90683a84f46aaf 100644
--- a/pkgs/development/python-modules/onnx/default.nix
+++ b/pkgs/development/python-modules/onnx/default.nix
@@ -46,7 +46,8 @@ buildPythonPackage rec {
   ];
 
   postPatch = ''
-    patchShebangs tools/protoc-gen-mypy.py
+    chmod +x tools/protoc-gen-mypy.sh.in
+    patchShebangs tools/protoc-gen-mypy.sh.in tools/protoc-gen-mypy.py
   '';
 
   preBuild = ''