diff --git a/mode/mutt.py b/mode/mutt.py
index 45a1f97..49e17fa 100644
--- a/mode/mutt.py
+++ b/mode/mutt.py
@@ -17,7 +17,7 @@ rules = [
 ]
 
 class HeaderGrammar(Grammar):
-    rules = [PatternRule('header', '^[^ ].*:')] + rules
+    rules = [PatternRule('header', '^[^ ][^:]*:')] + rules
 class BodyGrammar(Grammar): rules = rules
 class MuttGrammar(Grammar): 
     rules = [RegionRule('mutt', '^', HeaderGrammar, '^\n$', BodyGrammar, '')]