diff --git a/pre_commit/clientlib/validate_manifest.py b/pre_commit/clientlib/validate_manifest.py
index 2b7148fd..d11ce2b8 100644
--- a/pre_commit/clientlib/validate_manifest.py
+++ b/pre_commit/clientlib/validate_manifest.py
@@ -17,7 +17,7 @@ MANIFEST_JSON_SCHEMA = {
         'type': 'object',
         'properties': {
             'id': {'type': 'string'},
-            'always_run': {'type': 'boolean'},
+            'always_run': {'type': 'boolean', 'default': False},
             'name': {'type': 'string'},
             'description': {'type': 'string', 'default': ''},
             'entry': {'type': 'string'},
diff --git a/pre_commit/commands/run.py b/pre_commit/commands/run.py
index 82e494dd..f45e7089 100644
--- a/pre_commit/commands/run.py
+++ b/pre_commit/commands/run.py
@@ -72,19 +72,13 @@ def get_filenames(args, include_expr, exclude_expr):
 
 
 def _run_single_hook(hook, repo, args, write, skips=frozenset()):
-    filenames = []
-    # if the hook is marked as always_run, do not compute the files to run
-    # in that case, simply run the script once not matter the changes
-    compute_file_names = 'always_run' not in hook or not hook['always_run']
-
+    filenames = get_filenames(args, hook['files'], hook['exclude'])
     if hook['id'] in skips:
         _print_user_skipped(hook, write, args)
         return 0
-    elif compute_file_names:
-        filenames = get_filenames(args, hook['files'], hook['exclude'])
-        if not filenames:
-            _print_no_files_skipped(hook, write, args)
-            return 0
+    elif not filenames and not hook['always_run']:
+        _print_no_files_skipped(hook, write, args)
+        return 0
 
     # Print the hook and the dots first in case the hook takes hella long to
     # run.