diff --git a/pre_commit/clientlib.py b/pre_commit/clientlib.py
index 58031e8d..23d662ac 100644
--- a/pre_commit/clientlib.py
+++ b/pre_commit/clientlib.py
@@ -38,7 +38,7 @@ MANIFEST_HOOK_DICT = schema.Map(
 
     schema.Conditional(
         'files', schema.check_and(schema.check_string, schema.check_regex),
-        condition_key='always_run', condition_value=False, ensure_absent=True,
+        condition_key='always_run', condition_value=False,
     ),
 
     schema.Optional(
diff --git a/tests/clientlib_test.py b/tests/clientlib_test.py
index deaa7e9e..454824a9 100644
--- a/tests/clientlib_test.py
+++ b/tests/clientlib_test.py
@@ -187,6 +187,20 @@ def test_validate_manifest_main(args, expected_output):
             }],
             True,
         ),
+        (
+            # A regression in 0.13.5: always_run and files are permissible
+            # together (but meaningless).  In a future version upgrade this to
+            # an error
+            [{
+                'id': 'a',
+                'name': 'b',
+                'entry': 'c',
+                'language': 'python',
+                'files': '',
+                'always_run': True,
+            }],
+            True,
+        ),
     )
 )
 def test_valid_manifests(manifest_obj, expected):