diff --git a/lib/protocol/http/header/split.rb b/lib/protocol/http/header/split.rb
index 74c0356..cc3a67e 100644
--- a/lib/protocol/http/header/split.rb
+++ b/lib/protocol/http/header/split.rb
@@ -11,7 +11,7 @@ class Split < Array
 				COMMA = /\s*,\s*/
 				
 				def initialize(value)
-					if value
+					if value && value.respond_to?(:split)
 						super(value.split(COMMA))
 					else
 						super([])