diff --git a/check-grammar-crate.py b/check-grammar-crate.py
index 2a467ca84..cfba9c104 100755
--- a/check-grammar-crate.py
+++ b/check-grammar-crate.py
@@ -89,7 +89,7 @@ def run_rca(
         "--output-format=json",
         "--pr",
         "-I",
-        *include_grammars,
+        ",".join(include_grammars),
         "-p",
         repo_dir,
         "-o",