diff --git a/paramiko/pkey.py b/paramiko/pkey.py
index 1b4af010f..7d2be468c 100644
--- a/paramiko/pkey.py
+++ b/paramiko/pkey.py
@@ -273,7 +273,7 @@ def _read_private_key(self, tag, f, password=None):
             start += 1
         # find end
         end = start
-        while (lines[end].strip() != '-----END ' + tag + ' PRIVATE KEY-----') and (end < len(lines)):
+        while end < len(lines) and lines[end].strip() != '-----END ' + tag + ' PRIVATE KEY-----':
             end += 1
         # if we trudged to the end of the file, just try to cope.
         try: