diff --git a/pkg/dart2wasm/lib/translator.dart b/pkg/dart2wasm/lib/translator.dart
index 4e6c7e208f7..dfcd9baaf49 100644
--- a/pkg/dart2wasm/lib/translator.dart
+++ b/pkg/dart2wasm/lib/translator.dart
@@ -875,8 +875,20 @@ class Translator with KernelNodes {
         }
       } else if (to is w.RefType) {
         // Boxing
-        ClassInfo info = classInfo[boxedClasses[from]!]!;
+        Class cls = boxedClasses[from]!;
+        ClassInfo info = classInfo[cls]!;
         assert(info.struct.isSubtypeOf(to.heapType));
+
+        if (cls == boxedBoolClass) {
+          final constantType = w.RefType(info.struct, nullable: false);
+          b.if_([], [constantType]);
+          constants.instantiateConstant(b, BoolConstant(true), constantType);
+          b.else_();
+          constants.instantiateConstant(b, BoolConstant(false), constantType);
+          b.end();
+          return;
+        }
+
         w.Local temp = b.addLocal(from);
         b.local_set(temp);
         b.i32_const(info.classId);