diff --git a/lib/web_ui/lib/src/engine/html/surface.dart b/lib/web_ui/lib/src/engine/html/surface.dart
index b01ecbde7fb55..d1d816d29c4d8 100644
--- a/lib/web_ui/lib/src/engine/html/surface.dart
+++ b/lib/web_ui/lib/src/engine/html/surface.dart
@@ -1092,17 +1092,7 @@ abstract class PersistedContainerSurface extends PersistedSurface {
       for (int indexInOld = 0; indexInOld < oldChildCount; indexInOld += 1) {
         final PersistedSurface? oldChild = oldChildren[indexInOld];
         final bool childAlreadyClaimed = oldChild == null;
-        // After https://github.com/dart-lang/language/issues/1274 is
-        // implemented, `oldChild` will be promoted to non-nullable on the RHS
-        // of the `||`, so we won't need to null check it (and it will cause a
-        // build failure to try to do so).  Until then, we need to null check it
-        // in such a way that won't cause a build failure once the feature is
-        // implemented.  We can do that by casting to `dynamic`, and then
-        // relying on the call to `canUpdateAsMatch` implicitly downcasting to
-        // PersistentSurface.
-        // TODO(paulberry): remove this workaround once the feature is
-        // implemented.
-        if (childAlreadyClaimed || !newChild.canUpdateAsMatch(oldChild as dynamic)) {
+        if (childAlreadyClaimed || !newChild.canUpdateAsMatch(oldChild)) {
           continue;
         }
         allMatches.add(_PersistedSurfaceMatch(
diff --git a/lib/web_ui/lib/src/engine/semantics/semantics.dart b/lib/web_ui/lib/src/engine/semantics/semantics.dart
index 7a3df9c5b767b..36d05104066c2 100644
--- a/lib/web_ui/lib/src/engine/semantics/semantics.dart
+++ b/lib/web_ui/lib/src/engine/semantics/semantics.dart
@@ -875,16 +875,6 @@ class SemanticsObject {
         effectiveTransformIsIdentity = effectiveTransform.isIdentity();
       }
     } else if (!hasIdentityTransform) {
-      // After https://github.com/dart-lang/language/issues/1274 is implemented,
-      // `transform` will be promoted to non-nullable so we won't need to null
-      // check it (and it will cause a build failure to try to do so).  Until
-      // then, we need to null check it in such a way that won't cause a build
-      // failure once the feature is implemented.  We can do that using an
-      // explicit "if" test.
-      // TODO(paulberry): remove this check once the feature is implemented.
-      if (transform == null) { // ignore: unnecessary_null_comparison
-        throw 'impossible';
-      }
       effectiveTransform = Matrix4.fromFloat32List(transform);
       effectiveTransformIsIdentity = false;
     }