diff --git a/rosbridge_library/src/rosbridge_library/protocol.py b/rosbridge_library/src/rosbridge_library/protocol.py
index 829685a70..caccfe110 100644
--- a/rosbridge_library/src/rosbridge_library/protocol.py
+++ b/rosbridge_library/src/rosbridge_library/protocol.py
@@ -127,7 +127,13 @@ def incoming(self, message_string=""):
         if self.bson_only_mode:
             self.buffer.extend(message_string)
         else:
-            self.buffer = self.buffer + str(message_string)
+            if isinstance(message_string, bytes):
+                try:
+                    message_string = message_string.decode('utf-8')
+                except UnicodeDecodeError:
+                    self.log("error", "Received binary message with invalid UTF-8 encoding")
+                    return
+            self.buffer = self.buffer + message_string
         msg = None
 
         # take care of having multiple JSON-objects in receiving buffer