diff --git a/lib/jwt/encode.rb b/lib/jwt/encode.rb
index 546848c8..b72b0e72 100644
--- a/lib/jwt/encode.rb
+++ b/lib/jwt/encode.rb
@@ -38,7 +38,7 @@ def encoded_header_and_payload
     end
 
     def encode_header
-      encode_data(@headers.merge(@algorithm.header(signing_key: @key).merge))
+      encode_data(@headers.merge(@algorithm.header(signing_key: @key)))
     end
 
     def encode_payload