diff --git a/fsck.c b/fsck.c
index 6c855f8..da53cf4 100644
--- a/fsck.c
+++ b/fsck.c
@@ -139,6 +139,7 @@
 static int fsck_tree(struct tree *item, int strict, fsck_error error_func)
 {
 	int retval;
+	int has_null_sha1 = 0;
 	int has_full_path = 0;
 	int has_empty_name = 0;
 	int has_zero_pad = 0;
@@ -157,9 +158,12 @@
 	while (desc.size) {
 		unsigned mode;
 		const char *name;
+		const unsigned char *sha1;
 
-		tree_entry_extract(&desc, &name, &mode);
+		sha1 = tree_entry_extract(&desc, &name, &mode);
 
+		if (is_null_sha1(sha1))
+			has_null_sha1 = 1;
 		if (strchr(name, '/'))
 			has_full_path = 1;
 		if (!*name)
@@ -207,6 +211,8 @@
 	}
 
 	retval = 0;
+	if (has_null_sha1)
+		retval += error_func(&item->object, FSCK_WARN, "contains entries pointing to null sha1");
 	if (has_full_path)
 		retval += error_func(&item->object, FSCK_WARN, "contains full pathnames");
 	if (has_empty_name)
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index 5b8ebd8..5e36cc7 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -217,4 +217,30 @@
 	grep -q "error: sha1 mismatch 63ffffffffffffffffffffffffffffffffffffff" out
 '
 
+_bz='\0'
+_bz5="$_bz$_bz$_bz$_bz$_bz"
+_bz20="$_bz5$_bz5$_bz5$_bz5"
+
+test_expect_success 'fsck notices blob entry pointing to null sha1' '
+	(git init null-blob &&
+	 cd null-blob &&
+	 sha=$(printf "100644 file$_bz$_bz20" |
+	       git hash-object -w --stdin -t tree) &&
+	  git fsck 2>out &&
+	  cat out &&
+	  grep "warning.*null sha1" out
+	)
+'
+
+test_expect_success 'fsck notices submodule entry pointing to null sha1' '
+	(git init null-commit &&
+	 cd null-commit &&
+	 sha=$(printf "160000 submodule$_bz$_bz20" |
+	       git hash-object -w --stdin -t tree) &&
+	  git fsck 2>out &&
+	  cat out &&
+	  grep "warning.*null sha1" out
+	)
+'
+
 test_done