diff --git a/polkadot/scripts/gitlab/check_runtime.sh b/polkadot/scripts/gitlab/check_runtime.sh
index 10db3ce392..2169289b5c 100755
--- a/polkadot/scripts/gitlab/check_runtime.sh
+++ b/polkadot/scripts/gitlab/check_runtime.sh
@@ -89,7 +89,7 @@ then
 	EOT
 
 	# okay so now need to fetch the substrate repository and check whether spec_version or impl_version has changed there
-	SUBSTRATE_CLONE_DIR="$(mktemp -t -d substrate-XXX)"
+	SUBSTRATE_CLONE_DIR="$(mktemp -t -d substrate-XXXXXX)"
 	trap "rm -rf ${SUBSTRATE_CLONE_DIR}" INT QUIT TERM ABRT EXIT