diff --git a/lib/amq/protocol/client.rb b/lib/amq/protocol/client.rb
index 45b565e..62491da 100644
--- a/lib/amq/protocol/client.rb
+++ b/lib/amq/protocol/client.rb
@@ -174,7 +174,7 @@ def self.encode_body(body, channel, frame_size)
 
         # Otherwise String#slice on 1.9 will operate with code points,
         # and we need bytes. MK.
-        body.force_encoding("ASCII-8BIT") if RUBY_VERSION.to_f >= 1.9
+        body.force_encoding("ASCII-8BIT") if RUBY_VERSION.to_f >= 1.9 && body.encoding != Encoding::BINARY
 
         array = Array.new
         while body && !body.empty?