diff --git a/builtin-unpack-objects.c b/builtin-unpack-objects.c
index 8e831be476..bae00eabb0 100644
--- a/builtin-unpack-objects.c
+++ b/builtin-unpack-objects.c
@@ -181,10 +181,10 @@ static void write_cached_object(struct object *obj)
 static int check_object(struct object *obj, int type, void *data)
 {
 	if (!obj)
-		return 0;
+		return 1;
 
 	if (obj->flags & FLAG_WRITTEN)
-		return 1;
+		return 0;
 
 	if (type != OBJ_ANY && obj->type != type)
 		die("object type mismatch");
@@ -195,22 +195,24 @@ static int check_object(struct object *obj, int type, void *data)
 		if (type != obj->type || type <= 0)
 			die("object of unexpected type");
 		obj->flags |= FLAG_WRITTEN;
-		return 1;
+		return 0;
 	}
 
 	if (fsck_object(obj, 1, fsck_error_function))
 		die("Error in object");
-	if (!fsck_walk(obj, check_object, 0))
+	if (fsck_walk(obj, check_object, 0))
 		die("Error on reachable objects of %s", sha1_to_hex(obj->sha1));
 	write_cached_object(obj);
-	return 1;
+	return 0;
 }
 
 static void write_rest(void)
 {
 	unsigned i;
-	for (i = 0; i < nr_objects; i++)
-		check_object(obj_list[i].obj, OBJ_ANY, 0);
+	for (i = 0; i < nr_objects; i++) {
+		if (obj_list[i].obj)
+			check_object(obj_list[i].obj, OBJ_ANY, 0);
+	}
 }
 
 static void added_object(unsigned nr, enum object_type type,
diff --git a/t/t5531-deep-submodule-push.sh b/t/t5531-deep-submodule-push.sh
new file mode 100644
index 0000000000..65d8d474bc
--- /dev/null
+++ b/t/t5531-deep-submodule-push.sh
@@ -0,0 +1,35 @@
+#!/bin/sh
+
+test_description='unpack-objects'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	mkdir pub.git &&
+	GIT_DIR=pub.git git init --bare
+	GIT_DIR=pub.git git config receive.fsckobjects true &&
+	mkdir work &&
+	(
+		cd work &&
+		git init &&
+		mkdir -p gar/bage &&
+		(
+			cd gar/bage &&
+			git init &&
+			>junk &&
+			git add junk &&
+			git commit -m "Initial junk"
+		) &&
+		git add gar/bage &&
+		git commit -m "Initial superproject"
+	)
+'
+
+test_expect_success push '
+	(
+		cd work &&
+		git push ../pub.git master
+	)
+'
+
+test_done