diff --git a/.kokoro/tests/run_tests.sh b/.kokoro/tests/run_tests.sh
index 692bf93e750..6527e8b2469 100755
--- a/.kokoro/tests/run_tests.sh
+++ b/.kokoro/tests/run_tests.sh
@@ -22,9 +22,15 @@ shopt -s globstar
 
 DIFF_FROM=""
 
-# `--only-diff-master will only run tests on project changes from the master branch.
+# `--only-diff-master will only run tests on project changes on the last common commit from the master branch.
 if [[ $* == *--only-diff-master* ]]; then
-    DIFF_FROM="origin/master.."
+  git diff --quiet "origin/master..." .kokoro/tests .kokoro/docker
+  CHANGED=$?
+  if [[ "$CHANGED" -eq 0 ]]; then
+    DIFF_FROM="origin/master..."
+  else
+    echo "Changes to .kokoro/test or .kokoro docker detected. Running full tests."
+  fi
 fi
 
 # `--only-diff-master will only run tests on project changes from the previous commit.