diff --git a/src/mapi/glapi/gen/glX_proto_send.py b/src/mapi/glapi/gen/glX_proto_send.py
index bec0222..20137df 100644
--- a/src/mapi/glapi/gen/glX_proto_send.py
+++ b/src/mapi/glapi/gen/glX_proto_send.py
@@ -683,7 +683,9 @@ generic_%u_byte( GLint rop, const void * ptr )
 
 				elif output and not f.reply_always_array:
 					if not output.is_image():
-						print '        if (%s_data_length(reply) == 0)' % (xcb_name)
+						print '        // the XXX_data_length() xcb function name is misleading, it returns the number'
+						print '        // of elements, not the lenght of the data part. A single element is embedded.'
+						print '        if (%s_data_length(reply) == 1)' % (xcb_name)
 						print '            (void)memcpy(%s, &reply->datum, sizeof(reply->datum));' % (output.name)
 						print '        else'
 					print '        (void)memcpy(%s, %s_data(reply), %s_data_length(reply) * sizeof(%s));' % (output.name, xcb_name, xcb_name, output.get_base_type_string())