diff --git a/fs/ext4/fsmap.c b/fs/ext4/fsmap.c
index 37347ba..d1ef651 100644
--- a/fs/ext4/fsmap.c
+++ b/fs/ext4/fsmap.c
@@ -486,6 +486,8 @@
 		keys[0].fmr_physical = bofs;
 	if (keys[1].fmr_physical >= eofs)
 		keys[1].fmr_physical = eofs - 1;
+	if (keys[1].fmr_physical < keys[0].fmr_physical)
+		return 0;
 	start_fsb = keys[0].fmr_physical;
 	end_fsb = keys[1].fmr_physical;