diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index b0ff34b..65338a1 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -185,6 +185,7 @@
 			split = alloc_extent_map(GFP_NOFS);
 		if (!split2)
 			split2 = alloc_extent_map(GFP_NOFS);
+		BUG_ON(!split || !split2);
 
 		write_lock(&em_tree->lock);
 		em = lookup_extent_mapping(em_tree, start, len);