diff --git a/test/test_upload.c b/test/test_upload.c
index cd35b4f..e66baa6 100644
--- a/test/test_upload.c
+++ b/test/test_upload.c
@@ -371,7 +371,7 @@ static int load_file_contents()
 
 		files[i].file_buff = mmap(NULL, file_size, PROT_READ, \
 					MAP_SHARED, files[i].fd, 0);
-		if (files[i].file_buff == NULL)
+		if (files[i].file_buff == MAP_FAILED)
 		{
 			fprintf(stderr, "file: "__FILE__", line: %d, " \
 				"mmap file %s fail, " \