diff --git a/src/codedump.c b/src/codedump.c
index c7b81971b..292527f27 100644
--- a/src/codedump.c
+++ b/src/codedump.c
@@ -630,6 +630,7 @@ void
 mrb_codedump_all_file(mrb_state *mrb, struct RProc *proc, FILE *out)
 {
   codedump_recur(mrb, proc->body.irep, out);
+  fflush(out);
 }
 
 #endif