diff --git a/parse.y b/parse.y
index 410bbdd759..3c76d99585 100644
--- a/parse.y
+++ b/parse.y
@@ -11057,6 +11057,7 @@ parser_compile_error(struct parser_params *parser, const char *fmt, ...)
 {
     va_list ap;
 
+    rb_io_flush(parser->debug_output);
     parser->error_p = 1;
     va_start(ap, fmt);
     parser->error_buffer =