diff --git a/.ci/magic-modules/generate-terraform.sh b/.ci/magic-modules/generate-terraform.sh
index cbc80dd03857..9bf7e0c3b9e7 100755
--- a/.ci/magic-modules/generate-terraform.sh
+++ b/.ci/magic-modules/generate-terraform.sh
@@ -49,7 +49,11 @@ fi
 
 pushd "build/$SHORT_NAME"
 
-GO111MODULE=on go mod vendor
+# go mod vendor is a very expensive operation.
+# If no changes, avoid running.
+if git diff-index --quiet HEAD --; then
+  GO111MODULE=on go mod vendor
+fi
 
 # These config entries will set the "committer".
 git config --global user.email "magic-modules@google.com"