diff --git a/Lib/imaplib.py b/Lib/imaplib.py
index 826eea2..f813ece 100644
--- a/Lib/imaplib.py
+++ b/Lib/imaplib.py
@@ -1409,7 +1409,7 @@
     be in the correct format.
     """
 
-    if isinstance(date_time, (int, float)):
+    if isinstance(date_time, (int, long, float)):
         tt = time.localtime(date_time)
     elif isinstance(date_time, (tuple, time.struct_time)):
         tt = date_time