diff --git a/security/tomoyo/mount.c b/security/tomoyo/mount.c
index 162a864..9fc2e15 100644
--- a/security/tomoyo/mount.c
+++ b/security/tomoyo/mount.c
@@ -138,7 +138,7 @@
 	}
 	if (need_dev) {
 		/* Get mount point or device file. */
-		if (kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
+		if (!dev_name || kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
 			error = -ENOENT;
 			goto out;
 		}