diff --git a/Lib/email/Header.py b/Lib/email/Header.py
index 7f2b444..21acaf1 100644
--- a/Lib/email/Header.py
+++ b/Lib/email/Header.py
@@ -411,7 +411,7 @@
         # syntax; we just try to break on semi-colons, then commas, then
         # whitespace.
         for ch in splitchars:
-            if line.find(ch) >= 0:
+            if ch in line:
                 break
         else:
             # There's nothing useful to split the line on, not even spaces, so