diff --git a/jpegoptim.c b/jpegoptim.c
index f586947..ad44a1a 100644
--- a/jpegoptim.c
+++ b/jpegoptim.c
@@ -614,7 +614,7 @@ int optimize(FILE *log_fh, const char *filename, const char *newname,
 	}
 
 	/* prepare to decompress */
-	if (stdin_mode) {
+	if (stdin_mode || stdout_mode) {
 		if (inbuffer)
 			free(inbuffer);
 		inbuffersize=65536;