diff --git a/canopen/sdo/client.py b/canopen/sdo/client.py
index 05a0276d..44159c49 100644
--- a/canopen/sdo/client.py
+++ b/canopen/sdo/client.py
@@ -406,7 +406,8 @@ def write(self, b):
             res_command, = struct.unpack("B", response[0:1])
             if res_command & 0xE0 != RESPONSE_SEGMENT_DOWNLOAD:
                 raise SdoCommunicationError(
-                    "Unexpected response 0x%02X (expected 0x%02X)" % res_command)
+                    "Unexpected response 0x%02X (expected 0x%02X)" %
+                    (res_command, RESPONSE_SEGMENT_DOWNLOAD))
         # Advance position
         self.pos += bytes_sent
         return bytes_sent