diff --git a/es2panda/test/runner.py b/es2panda/test/runner.py
index ea03d3ac80b9a294c181c938b567682d2a7d1761..572fcfd1868dff6fe2750ed315832ad261286ae6 100755
--- a/es2panda/test/runner.py
+++ b/es2panda/test/runner.py
@@ -797,7 +797,7 @@ class CompilerTest(Test):
         test_abc_path = path.join(runner.build_dir, test_abc_name)
         es2abc_cmd = runner.cmd_prefix + [runner.es2panda]
         es2abc_cmd.extend(self.flags)
-        es2abc_cmd.extend(["--output=" + test_abc_path])
+        es2abc_cmd.extend(['%s%s' % ("--output=", test_abc_path)])
         es2abc_cmd.append(self.path)
         self.log_cmd(es2abc_cmd)