diff --git a/pre_commit/commands/hook_impl.py b/pre_commit/commands/hook_impl.py
index 0ec303564..ada8ed383 100644
--- a/pre_commit/commands/hook_impl.py
+++ b/pre_commit/commands/hook_impl.py
@@ -11,7 +11,9 @@
 from pre_commit.parse_shebang import normalize_cmd
 from pre_commit.store import Store
 
-Z40 = '0' * 40
+
+def _is_zero_oid(oid: str) -> bool:
+    return bool(oid) and all(character == '0' for character in oid)
 
 
 def _run_legacy(
@@ -128,9 +130,9 @@ def _pre_push_ns(
     for line in stdin.decode().splitlines():
         parts = line.rsplit(maxsplit=3)
         local_branch, local_sha, remote_branch, remote_sha = parts
-        if local_sha == Z40:
+        if _is_zero_oid(local_sha):
             continue
-        elif remote_sha != Z40 and _rev_exists(remote_sha):
+        elif not _is_zero_oid(remote_sha) and _rev_exists(remote_sha):
             return _ns(
                 'pre-push', color,
                 from_ref=remote_sha, to_ref=local_sha,
diff --git a/tests/commands/hook_impl_test.py b/tests/commands/hook_impl_test.py
index 9aa93af53..31a0d4847 100644
--- a/tests/commands/hook_impl_test.py
+++ b/tests/commands/hook_impl_test.py
@@ -18,6 +18,8 @@
 from testing.util import cwd
 from testing.util import git_commit
 
+ZERO_OID = '0' * 40
+
 
 def test_validate_config_file_exists(tmpdir):
     cfg = tmpdir.join(C.CONFIG_FILE).ensure()
@@ -284,12 +286,14 @@ def test_run_ns_pre_push_updating_branch(push_example):
     assert ns.all_files is False
 
 
-def test_run_ns_pre_push_new_branch(push_example):
+@pytest.mark.parametrize('zero_oid_length', (40, 64))
+def test_run_ns_pre_push_new_branch(push_example, zero_oid_length):
     src, src_head, clone, clone_head = push_example
 
     with cwd(clone):
         args = ('origin', src)
-        stdin = f'HEAD {clone_head} refs/heads/b {hook_impl.Z40}\n'.encode()
+        zero_oid = '0' * zero_oid_length
+        stdin = f'HEAD {clone_head} refs/heads/b {zero_oid}\n'.encode()
         ns = hook_impl._run_ns('pre-push', False, args, stdin)
 
     assert ns is not None
@@ -302,7 +306,7 @@ def test_run_ns_pre_push_new_branch_existing_rev(push_example):
 
     with cwd(clone):
         args = ('origin', src)
-        stdin = f'HEAD {src_head} refs/heads/b2 {hook_impl.Z40}\n'.encode()
+        stdin = f'HEAD {src_head} refs/heads/b2 {ZERO_OID}\n'.encode()
         ns = hook_impl._run_ns('pre-push', False, args, stdin)
 
     assert ns is None
@@ -313,7 +317,7 @@ def test_run_ns_pre_push_ref_with_whitespace(push_example):
 
     with cwd(clone):
         args = ('origin', src)
-        line = f'HEAD^{{/ }} {src_head} refs/heads/b2 {hook_impl.Z40}\n'
+        line = f'HEAD^{{/ }} {src_head} refs/heads/b2 {ZERO_OID}\n'
         stdin = line.encode()
         ns = hook_impl._run_ns('pre-push', False, args, stdin)
 
@@ -329,19 +333,21 @@ def test_pushing_orphan_branch(push_example):
 
     with cwd(clone):
         args = ('origin', src)
-        stdin = f'HEAD {clone_rev} refs/heads/b2 {hook_impl.Z40}\n'.encode()
+        stdin = f'HEAD {clone_rev} refs/heads/b2 {ZERO_OID}\n'.encode()
         ns = hook_impl._run_ns('pre-push', False, args, stdin)
 
     assert ns is not None
     assert ns.all_files is True
 
 
-def test_run_ns_pre_push_deleting_branch(push_example):
+@pytest.mark.parametrize('zero_oid_length', (40, 64))
+def test_run_ns_pre_push_deleting_branch(push_example, zero_oid_length):
     src, src_head, clone, _ = push_example
 
     with cwd(clone):
         args = ('origin', src)
-        stdin = f'(delete) {hook_impl.Z40} refs/heads/b {src_head}'.encode()
+        zero_oid = '0' * zero_oid_length
+        stdin = f'(delete) {zero_oid} refs/heads/b {src_head}'.encode()
         ns = hook_impl._run_ns('pre-push', False, args, stdin)
 
     assert ns is None
@@ -350,7 +356,7 @@ def test_run_ns_pre_push_deleting_branch(push_example):
 def test_hook_impl_main_noop_pre_push(cap_out, store, push_example):
     src, src_head, clone, _ = push_example
 
-    stdin = f'(delete) {hook_impl.Z40} refs/heads/b {src_head}'.encode()
+    stdin = f'(delete) {ZERO_OID} refs/heads/b {src_head}'.encode()
     with mock.patch.object(sys.stdin.buffer, 'read', return_value=stdin):
         with cwd(clone):
             write_config('.', sample_local_config())