diff --git a/lib/awesome_print/formatters/hash_formatter.rb b/lib/awesome_print/formatters/hash_formatter.rb
index <HASH>..<HASH> 100644
--- a/lib/awesome_print/formatters/hash_formatter.rb
+++ b/lib/awesome_print/formatters/hash_formatter.rb
@@ -32,7 +32,7 @@ module AwesomePrint
       end
 
       def multiline_hash
-        "{\n" << printable_hash.join(",\n") << "\n#{outdent}}"
+        ["{\n", printable_hash.join(",\n"), "\n#{outdent}}"].join
       end
 
       def simple_hash
Multilines should use string#join rather than concat <<