diff --git a/rbtools/clients/git.py b/rbtools/clients/git.py
index 1df274f2725abaef2de90d89c15c31083e7b324f..ff634737be5a3de5f2eb8eb496056fbdc2dac1d0 100644
--- a/rbtools/clients/git.py
+++ b/rbtools/clients/git.py
@@ -365,9 +365,14 @@ class GitClient(SCMClient):
                                    'upgraded to version 1.5.4 or later.')
 
         # Okay, maybe Perforce (git-p4).
-        git_p4_ref = os.path.join(self._git_dir, 'refs', 'remotes', 'p4',
-                                  'master')
-        if os.path.exists(git_p4_ref):
+        git_p4_ref = self._execute([self.git,
+                                    'show-ref',
+                                    '--verify',
+                                    'refs/remotes/p4/master'],
+                                   none_on_ignored_error=True,
+                                   ignore_errors=True)
+
+        if git_p4_ref:
             data = self._execute([self.git, 'config', '--get', 'git-p4.port'],
                                  ignore_errors=True)
             m = re.search(r'(.+)', data)