diff --git a/json-rpc-shell.c b/json-rpc-shell.c
index 7d104a2..77a9fa9 100644
--- a/json-rpc-shell.c
+++ b/json-rpc-shell.c
@@ -1958,7 +1958,7 @@ backend_ws_on_frame (void *user_data, const struct ws_parser *parser)
 		return true;
 
 	if (self->message_opcode == WS_OPCODE_TEXT
-	 && !utf8_validate (self->parser.input.str, self->parser.input.len))
+	 && !utf8_validate (self->message_data.str, self->message_data.len))
 		return backend_ws_fail (self, WS_STATUS_INVALID_PAYLOAD_DATA);
 
 	bool result = backend_ws_on_message (self, self->message_opcode,