diff -uriN btrfs-progs-v4.0.1.orig/ctree.c btrfs-progs-v4.0.1/ctree.c
--- btrfs-progs-v4.0.1.orig/ctree.c	2015-06-19 03:43:12.000000000 -0500
+++ btrfs-progs-v4.0.1/ctree.c	2015-06-21 05:15:35.000000000 -0500
@@ -2588,14 +2588,16 @@
 	int ret = 0;
 
 	nritems = btrfs_header_nritems(parent);
-	if (slot != nritems -1) {
-		memmove_extent_buffer(parent,
-			      btrfs_node_key_ptr_offset(slot),
-			      btrfs_node_key_ptr_offset(slot + 1),
-			      sizeof(struct btrfs_key_ptr) *
-			      (nritems - slot - 1));
+	if (nritems > 0) {
+		if (slot < nritems -1) {
+			memmove_extent_buffer(parent,
+					 btrfs_node_key_ptr_offset(slot),
+					 btrfs_node_key_ptr_offset(slot + 1),
+					 sizeof(struct btrfs_key_ptr) *
+					 (nritems - slot - 1));
+		}
+		nritems--;
 	}
-	nritems--;
 	btrfs_set_header_nritems(parent, nritems);
 	if (nritems == 0 && parent == root->node) {
 		BUG_ON(btrfs_header_level(root->node) != 1);