diff --git a/fast-import.c b/fast-import.c
index 8328e004bb..194116be6f 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -520,10 +520,11 @@ static struct tree_entry* new_tree_entry()
 		unsigned int n = tree_entry_alloc;
 		total_allocd += n * sizeof(struct tree_entry);
 		avail_tree_entry = e = xmalloc(n * sizeof(struct tree_entry));
-		while (n--) {
+		while (n-- > 1) {
 			*((void**)e) = e + 1;
 			e++;
 		}
+		*((void*)e) = NULL;
 	}
 
 	e = avail_tree_entry;