diff --git a/src/applications/fact/chart/PhabricatorFactChartFunction.php b/src/applications/fact/chart/PhabricatorFactChartFunction.php
--- a/src/applications/fact/chart/PhabricatorFactChartFunction.php
+++ b/src/applications/fact/chart/PhabricatorFactChartFunction.php
@@ -29,6 +29,7 @@
     $key_id = id(new PhabricatorFactKeyDimension())
       ->newDimensionID($fact->getKey());
     if (!$key_id) {
+      $this->map = array();
       return;
     }