diff --git a/src/api/environment.cc b/src/api/environment.cc
index a574b916fe6f00..210abb94295f53 100644
--- a/src/api/environment.cc
+++ b/src/api/environment.cc
@@ -27,6 +27,7 @@ using v8::Object;
 using v8::ObjectTemplate;
 using v8::Private;
 using v8::PropertyDescriptor;
+using v8::SealHandleScope;
 using v8::String;
 using v8::Value;
 
@@ -378,10 +379,13 @@ Environment* CreateEnvironment(
 }
 
 void FreeEnvironment(Environment* env) {
+  Isolate::DisallowJavascriptExecutionScope disallow_js(env->isolate(),
+      Isolate::DisallowJavascriptExecutionScope::THROW_ON_FAILURE);
   {
-    // TODO(addaleax): This should maybe rather be in a SealHandleScope.
-    HandleScope handle_scope(env->isolate());
+    HandleScope handle_scope(env->isolate());  // For env->context().
     Context::Scope context_scope(env->context());
+    SealHandleScope seal_handle_scope(env->isolate());
+
     env->set_stopping(true);
     env->stop_sub_worker_contexts();
     env->RunCleanup();
diff --git a/src/node_worker.cc b/src/node_worker.cc
index 403c054ab21e77..fa68fe88dc89f4 100644
--- a/src/node_worker.cc
+++ b/src/node_worker.cc
@@ -274,10 +274,6 @@ void Worker::Run() {
         this->env_ = nullptr;
       }
 
-      // TODO(addaleax): Try moving DisallowJavascriptExecutionScope into
-      // FreeEnvironment().
-      Isolate::DisallowJavascriptExecutionScope disallow_js(isolate_,
-          Isolate::DisallowJavascriptExecutionScope::THROW_ON_FAILURE);
       env_.reset();
     });
 
diff --git a/test/addons/worker-addon/binding.cc b/test/addons/worker-addon/binding.cc
index 01c857c43ebcfc..63728fa9a4b76d 100644
--- a/test/addons/worker-addon/binding.cc
+++ b/test/addons/worker-addon/binding.cc
@@ -6,10 +6,13 @@
 #include <uv.h>
 
 using v8::Context;
+using v8::Function;
 using v8::HandleScope;
 using v8::Isolate;
 using v8::Local;
+using v8::MaybeLocal;
 using v8::Object;
+using v8::String;
 using v8::Value;
 
 size_t count = 0;
@@ -31,6 +34,18 @@ void Dummy(void*) {
 
 void Cleanup(void* str) {
   printf("%s ", static_cast<const char*>(str));
+
+  // Check that calling into JS fails.
+  Isolate* isolate = Isolate::GetCurrent();
+  HandleScope handle_scope(isolate);
+  assert(isolate->InContext());
+  Local<Context> context = isolate->GetCurrentContext();
+  MaybeLocal<Value> call_result =
+      context->Global()->Get(
+          context, String::NewFromUtf8Literal(isolate, "Object"))
+              .ToLocalChecked().As<Function>()->Call(
+                  context, v8::Null(isolate), 0, nullptr);
+  assert(call_result.IsEmpty());
 }
 
 void Initialize(Local<Object> exports,