diff --git a/dkim/__init__.py b/dkim/__init__.py
index 3eb6bc2..dca0e0a 100644
--- a/dkim/__init__.py
+++ b/dkim/__init__.py
@@ -296,10 +296,10 @@ class DKIM(object):
         return False
 
     # Currently, we only validate the first DKIM-Signature line found.
-    #try:
-    sig = parse_tag_value(sigheaders[0][1])
-    #except InvalidTagValueList,e:
-    #    raise MessageFormatError(e)
+    try:
+        sig = parse_tag_value(sigheaders[0][1])
+    except InvalidTagValueList,e:
+        raise MessageFormatError(e)
 
     sig = parse_tag_value(sigheaders[0][1])
     logger = self.logger