diff --git a/packages/flutter/lib/widgets/mimic.dart b/packages/flutter/lib/widgets/mimic.dart
index eb6aa22cf8..df92c5e211 100644
--- a/packages/flutter/lib/widgets/mimic.dart
+++ b/packages/flutter/lib/widgets/mimic.dart
@@ -98,7 +98,9 @@ class Mimic extends GlobalKeyWatcher {
   void _setMimicable(widget) {
     if (_mimicable != widget) {
       _stopMimic();
-      widget.startMimic();
+      if (widget != null) {
+        widget.startMimic();
+      }
     }
     setState(() {
       _mimicable = widget;