diff --git a/builtin-update-index.c b/builtin-update-index.c
index 325cd0944d..ef50243452 100644
--- a/builtin-update-index.c
+++ b/builtin-update-index.c
@@ -490,7 +490,7 @@ int cmd_update_index(int argc, const char **argv, char **envp)
 	git_config(git_default_config);
 
 	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
-	lock_file = xmalloc(sizeof(struct lock_file));
+	lock_file = xcalloc(1, sizeof(struct lock_file));
 
 	newfd = hold_lock_file_for_update(lock_file, get_index_file());
 	if (newfd < 0)
diff --git a/builtin-write-tree.c b/builtin-write-tree.c
index c3aac36024..70e9b6fcc6 100644
--- a/builtin-write-tree.c
+++ b/builtin-write-tree.c
@@ -16,7 +16,7 @@ int write_tree(unsigned char *sha1, int missing_ok, const char *prefix)
 	int entries, was_valid, newfd;
 
 	/* We can't free this memory, it becomes part of a linked list parsed atexit() */
-	struct lock_file *lock_file = xmalloc(sizeof(struct lock_file));
+	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
 
 	newfd = hold_lock_file_for_update(lock_file, get_index_file());