diff --git a/src/common/jsonrpc2/server.py b/src/common/jsonrpc2/server.py
index ac0a27d..27bc4ee 100644
--- a/src/common/jsonrpc2/server.py
+++ b/src/common/jsonrpc2/server.py
@@ -151,7 +151,7 @@ async def handler(request: ws.WebSocketRequest):
             exc = e
         except KeyError as e:
             err = Error.METHOD_NOT_FOUND
-            err.data = str(e)
+            err.data = str(e).strip("'")
             exc = e
         except ws.ConnectionClosed as e:
             logger.critical('Going away', exc_info=e)