diff --git a/pkgs/development/python-modules/google-cloud-spanner/default.nix b/pkgs/development/python-modules/google-cloud-spanner/default.nix
index 3981cb83c107..3c5dcc432347 100644
--- a/pkgs/development/python-modules/google-cloud-spanner/default.nix
+++ b/pkgs/development/python-modules/google-cloud-spanner/default.nix
@@ -46,6 +46,10 @@ buildPythonPackage (finalAttrs: {
 
   build-system = [ setuptools ];
 
+  pythonRelaxDeps = [
+    "protobuf"
+  ];
+
   dependencies = [
     deprecated
     google-api-core