diff --git a/tools/build_protobuf b/tools/build_protobuf
index 91581c444..293c49f25 100755
--- a/tools/build_protobuf
+++ b/tools/build_protobuf
@@ -99,7 +99,7 @@ do_check() {
 
     cp -rT "$DESTDIR" "$TMPDIR"
     do_rebuild "$TMPDIR" "$@"
-    DIFF=$(diff -ur "$DESTDIR" "$TMPDIR")
+    DIFF=$(diff -ur --exclude __pycache__ "$DESTDIR" "$TMPDIR")
     rm -r "$TMPDIR"
     if [ -n "$DIFF" ]; then
         echo "$DIFF"