diff --git a/lib/src/polyfill.dart b/lib/src/polyfill.dart
index 389b89c..b65ec61 100644
--- a/lib/src/polyfill.dart
+++ b/lib/src/polyfill.dart
@@ -246,9 +246,7 @@
         replaceExprs.replaceRange(0, 1, defaultValues);
         return varDef;
       }
-      if (foundDef is VarDefinition) {
-        return _findTerminalVarDefinition(varDefs, foundDef);
-      }
+      return _findTerminalVarDefinition(varDefs, foundDef);
     } else {
       // Return real CSS property.
       return varDef;
diff --git a/lib/src/tree.dart b/lib/src/tree.dart
index 83e8b09..3af71dc 100644
--- a/lib/src/tree.dart
+++ b/lib/src/tree.dart
@@ -1736,9 +1736,7 @@
 
   @override
   HeightExpression? merged(DartStyleExpression newHeightExpr) {
-    if (newHeightExpr is DartStyleExpression &&
-        isHeight &&
-        newHeightExpr.isHeight) {
+    if (isHeight && newHeightExpr.isHeight) {
       return newHeightExpr as HeightExpression;
     }