diff --git a/frontend/cmd/assemble.c b/frontend/cmd/assemble.c
index b3cb34a..d38b722 100644
--- a/frontend/cmd/assemble.c
+++ b/frontend/cmd/assemble.c
@@ -29,7 +29,7 @@ static int assemble_file(const char *in_path, const char *out_path)
 		return -1;
 	}
 
-	FILE *out = fopen(out_path, "wb");
+	FILE *out = fopen(out_path, "w+b");
 	if (!out) {
 		b_err("cannot open output file '%s'", out_path);
 		b_i("reason: %s", strerror(errno));