diff --git a/frontend_tests/zjsunit/index.js b/frontend_tests/zjsunit/index.js
index 46f81cc86a..98dfa25c99 100644
--- a/frontend_tests/zjsunit/index.js
+++ b/frontend_tests/zjsunit/index.js
@@ -114,7 +114,13 @@ try {
         namespace.finish();
     }
 } catch (error) {
-    if (error.stack) {
+    if (process.env.USING_INSTRUMENTED_CODE) {
+        console.info(`
+    TEST FAILED! Before using the --coverage option please make sure that your
+    tests work under normal conditions.
+
+        `);
+    } else if (error.stack) {
         console.info(short_tb(error.stack));
     } else {
         console.info(error);
diff --git a/tools/test-js-with-node b/tools/test-js-with-node
index f7b808dd1d..ce0107cd1d 100755
--- a/tools/test-js-with-node
+++ b/tools/test-js-with-node
@@ -312,6 +312,7 @@ def run_tests_via_node_js() -> int:
 
     node_tests_cmd += test_files
     if options.coverage:
+        os.environ["USING_INSTRUMENTED_CODE"] = "TRUE"
         coverage_dir = os.path.join(ROOT_DIR, "var/node-coverage")
 
         nyc = os.path.join(ROOT_DIR, "node_modules/.bin/nyc")