diff --git a/py/h2o_wave/h2o_wave/server.py b/py/h2o_wave/h2o_wave/server.py
index 86cef17339..c00530672e 100644
--- a/py/h2o_wave/h2o_wave/server.py
+++ b/py/h2o_wave/h2o_wave/server.py
@@ -286,7 +286,7 @@ async def _register(self):
                 elapsed_time = current_time - start_time
                 if elapsed_time.seconds > connection_timeout:
                     logger.debug(f'Register: giving up after retrying for {connection_timeout} seconds')
-                    raise exception
+                    raise ConnectionError('Could not connect to Wave server. Make sure it is running.') from exception
                 await asyncio.sleep(1)
                 logger.debug('Register: retrying...')