diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index 93d938a..6094c5a 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -247,7 +247,7 @@
 	mst->total_dirty = cpu_to_le64(tmp64);
 
 	/*  The indexing LEB does not contribute to dark space */
-	tmp64 = (c->main_lebs - 1) * c->dark_wm;
+	tmp64 = ((long long)(c->main_lebs - 1) * c->dark_wm);
 	mst->total_dark = cpu_to_le64(tmp64);
 
 	mst->total_used = cpu_to_le64(UBIFS_INO_NODE_SZ);