diff --git a/tests/qtest/migration/migration-util.c b/tests/qtest/migration/migration-util.c
index 525bf1eed4..401fe27f00 100644
--- a/tests/qtest/migration/migration-util.c
+++ b/tests/qtest/migration/migration-util.c
@@ -284,6 +284,7 @@ bool probe_o_direct_support(const char *tmpfs)
 
     buf = qemu_try_memalign(len, len);
     g_assert(buf);
+    memset(buf, 0, len);
 
     ret = pwrite(fd, buf, len, offset);
     unlink(filename);