README.md in key_mapable-0.4.0 vs README.md in key_mapable-0.5.0

@@ -31,10 +31,10 @@
     # Map the value of `#name` to the key 'Name'.
     key_map(:name, 'Name')
 
     # Map the value of `#maybe_value` to the key 'GuaranteedValue'.
     # Transform the value by calling `#to_s` first.
-    key_map(:maybe_value, 'GuaranteedValue', -> (val) { val.to_s })
+    key_map(:maybe_value, 'GuaranteedValue', transform: ->(val) { val.to_s })
 
     # Map the key 'Name' to the value provided by the block.
     key_value('AConstant') { 'Foo' }
 
     # Map every item returned from `#rows`.