diff --git a/packages/flutter/lib/src/widgets/basic.dart b/packages/flutter/lib/src/widgets/basic.dart
index 26b179862d..fc7e18de85 100644
--- a/packages/flutter/lib/src/widgets/basic.dart
+++ b/packages/flutter/lib/src/widgets/basic.dart
@@ -1994,6 +1994,8 @@ class DefaultTextStyle extends InheritedWidget {
     TextOverflow overflow,
     Widget child
   }) {
+    assert(context != null);
+    assert(child != null);
     DefaultTextStyle parent = DefaultTextStyle.of(context);
     return new DefaultTextStyle(
       key: key,