diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 4be2d93c2a..87a113f7f2 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -287,7 +287,7 @@ jobs:
             pip install --user numpy==1.19.5
             # Older TF needs also older protobuf version.
             # https://github.com/rwth-i6/returnn/issues/1209
-            pip install --user protobuf==3.20.1
+            pip install --user "protobuf<=3.20.1"
           fi
         fi
         pip install --user -r requirements.txt | cat