diff --git a/lib/src/ffi.dart b/lib/src/ffi.dart
index dade9a9..e85d1f0 100644
--- a/lib/src/ffi.dart
+++ b/lib/src/ffi.dart
@@ -41,11 +41,11 @@ abstract class JSRef {
     if (cache.contains(obj)) return;
     if (obj is List) {
       cache.add(obj);
-      obj.forEach((e) => _callRecursive(e, cb, cache));
+      List.from(obj).forEach((e) => _callRecursive(e, cb, cache));
     }
     if (obj is Map) {
       cache.add(obj);
-      obj.values.forEach((e) => _callRecursive(e, cb, cache));
+      obj.values.toList().forEach((e) => _callRecursive(e, cb, cache));
     }
     if (obj is JSRef) {
       cb(obj);
diff --git a/pubspec.lock b/pubspec.lock
index 02fb490..d828156 100644
--- a/pubspec.lock
+++ b/pubspec.lock
@@ -151,4 +151,4 @@ packages:
     version: "2.1.0-nullsafety.5"
 sdks:
   dart: ">=2.12.0-0.0 <3.0.0"
-  flutter: ">=1.20.0 <2.0.0"
+  flutter: ">=1.20.0"