diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index b401654011a..8a1e61545f4 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -1747,8 +1747,8 @@ int ocfs2_write_begin_nolock(struct address_space *mapping,
 	 * we know zeros will only be needed in the first and/or last cluster.
 	 */
 	if (clusters_to_alloc || extents_to_split ||
-	    wc->w_desc[0].c_needs_zero ||
-	    wc->w_desc[wc->w_clen - 1].c_needs_zero)
+	    (wc->w_clen && (wc->w_desc[0].c_needs_zero ||
+			    wc->w_desc[wc->w_clen - 1].c_needs_zero)))
 		cluster_of_pages = 1;
 	else
 		cluster_of_pages = 0;