diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index 0ef10f04ea..1618f2078c 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -715,6 +715,7 @@ phutil_register_library_map(array(
     'DifferentialUnitTestResult' => 'applications/differential/constants/DifferentialUnitTestResult.php',
     'DifferentialUpdateRevisionConduitAPIMethod' => 'applications/differential/conduit/DifferentialUpdateRevisionConduitAPIMethod.php',
     'DifferentialViewState' => 'applications/differential/storage/DifferentialViewState.php',
+    'DifferentialViewStateGarbageCollector' => 'applications/differential/garbagecollector/DifferentialViewStateGarbageCollector.php',
     'DifferentialViewStateQuery' => 'applications/differential/query/DifferentialViewStateQuery.php',
     'DiffusionAuditorDatasource' => 'applications/diffusion/typeahead/DiffusionAuditorDatasource.php',
     'DiffusionAuditorFunctionDatasource' => 'applications/diffusion/typeahead/DiffusionAuditorFunctionDatasource.php',
@@ -6803,6 +6804,7 @@ phutil_register_library_map(array(
       'DifferentialDAO',
       'PhabricatorPolicyInterface',
     ),
+    'DifferentialViewStateGarbageCollector' => 'PhabricatorGarbageCollector',
     'DifferentialViewStateQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'DiffusionAuditorDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
     'DiffusionAuditorFunctionDatasource' => 'PhabricatorTypeaheadCompositeDatasource',
diff --git a/src/applications/differential/garbagecollector/DifferentialViewStateGarbageCollector.php b/src/applications/differential/garbagecollector/DifferentialViewStateGarbageCollector.php
new file mode 100644
index 0000000000..e862de22f1
--- /dev/null
+++ b/src/applications/differential/garbagecollector/DifferentialViewStateGarbageCollector.php
@@ -0,0 +1,29 @@
+<?php
+
+final class DifferentialViewStateGarbageCollector
+  extends PhabricatorGarbageCollector {
+
+  const COLLECTORCONST = 'differential.viewstate';
+
+  public function getCollectorName() {
+    return pht('Differential View States');
+  }
+
+  public function getDefaultRetentionPolicy() {
+    return phutil_units('180 days in seconds');
+  }
+
+  protected function collectGarbage() {
+    $table = new DifferentialViewState();
+    $conn = $table->establishConnection('w');
+
+    queryfx(
+      $conn,
+      'DELETE FROM %R WHERE dateModified < %d LIMIT 100',
+      $table,
+      $this->getGarbageEpoch());
+
+    return ($conn->getAffectedRows() == 100);
+  }
+
+}
diff --git a/src/applications/differential/storage/DifferentialViewState.php b/src/applications/differential/storage/DifferentialViewState.php
index 763edd8460..101061f379 100644
--- a/src/applications/differential/storage/DifferentialViewState.php
+++ b/src/applications/differential/storage/DifferentialViewState.php
@@ -23,6 +23,9 @@ final class DifferentialViewState
         'key_object' => array(
           'columns' => array('objectPHID'),
         ),
+        'key_modified' => array(
+          'columns' => array('dateModified'),
+        ),
       ),
     ) + parent::getConfiguration();
   }