diff --git a/pre_commit/clientlib/validate_config.py b/pre_commit/clientlib/validate_config.py
index 1da54f91..8991850e 100644
--- a/pre_commit/clientlib/validate_config.py
+++ b/pre_commit/clientlib/validate_config.py
@@ -32,6 +32,7 @@ CONFIG_JSON_SCHEMA = {
                     'type': 'object',
                     'properties': {
                         'id': {'type': 'string'},
+                        'always_run': {'type': 'boolean'},
                         'files': {'type': 'string'},
                         'exclude': {'type': 'string'},
                         'language_version': {'type': 'string'},
diff --git a/pre_commit/clientlib/validate_manifest.py b/pre_commit/clientlib/validate_manifest.py
index 094c8e5d..2b7148fd 100644
--- a/pre_commit/clientlib/validate_manifest.py
+++ b/pre_commit/clientlib/validate_manifest.py
@@ -17,6 +17,7 @@ MANIFEST_JSON_SCHEMA = {
         'type': 'object',
         'properties': {
             'id': {'type': 'string'},
+            'always_run': {'type': 'boolean'},
             '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 e01c7f9f..82e494dd 100644
--- a/pre_commit/commands/run.py
+++ b/pre_commit/commands/run.py
@@ -72,13 +72,19 @@ def get_filenames(args, include_expr, exclude_expr):
 
 
 def _run_single_hook(hook, repo, args, write, skips=frozenset()):
-    filenames = get_filenames(args, hook['files'], hook['exclude'])
+    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']
+
     if hook['id'] in skips:
         _print_user_skipped(hook, write, args)
         return 0
-    elif not filenames:
-        _print_no_files_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
 
     # Print the hook and the dots first in case the hook takes hella long to
     # run.