diff --git a/ext/mbstring/tests/bug20087.phpt b/ext/mbstring/tests/bug20087.phpt
new file mode 100644
index 00000000000..e45ab840207
--- /dev/null
+++ b/ext/mbstring/tests/bug20087.phpt
@@ -0,0 +1,21 @@
+--TEST--
+bug #20087 (Assertion failure)
+--SKIPIF--
+<?php include('skipif.inc'); ?>
+--POST--
+--GET--
+--FILE--
+<?php
+ini_set('include_path','.');
+include_once('common.inc');
+var_dump(mb_parse_str("testmoo"));
+var_dump($testmoo);
+var_dump(mb_parse_str("test=moo"));
+var_dump($test);
+?>
+--EXPECT--
+bool(true)
+string(0) ""
+bool(true)
+string(3) "moo"
+