diff --git a/lib/map/struct.rb b/lib/map/struct.rb
index d1159d6..cd384d9 100644
--- a/lib/map/struct.rb
+++ b/lib/map/struct.rb
@@ -19,6 +19,9 @@ def method_missing(method, *args, &block)
         when /\?$/
           key = method.chomp('?')
           value = @map.has?( key )
+        when /\!$/
+          key = method.chomp('!')
+          value = @map.has?( key )
         else
           key = method
           raise(IndexError, key) unless @map.has_key?(key)