diff --git a/testcases/test-dev-bug-string-replace-undefined-cap.js b/testcases/test-dev-bug-string-replace-undefined-cap.js
new file mode 100644
index 00000000..57b46952
--- /dev/null
+++ b/testcases/test-dev-bug-string-replace-undefined-cap.js
@@ -0,0 +1,26 @@
+
+/*===
+foo
+foo
+fo
+fo
+f
+f
+===*/
+
+/* Undefined captures were not skipped correctly. */
+
+try {
+    print('foo'.replace(/(o)|(o)/, '$1'));
+    print('foo'.replace(/(o)|(o)/, '$01'));
+
+    // capture 2 not found, matching string should be replaced with empty;
+    // with the bug, the first one would print "f2o".
+    print('foo'.replace(/(o)|(o)/, '$2'));
+    print('foo'.replace(/(o)|(o)/, '$02'));
+    print('foo'.replace(/(o)|(o)/g, '$2'));
+    print('foo'.replace(/(o)|(o)/g, '$02'));
+} catch (e) {
+    print(e);
+}
+