diff --git a/libdeno/binding.cc b/libdeno/binding.cc
index 9e6398d238..7bc1a03972 100644
--- a/libdeno/binding.cc
+++ b/libdeno/binding.cc
@@ -413,7 +413,7 @@ void deno_init() {
   v8::V8::Initialize();
 }
 
-void* deno_get_data(Deno* d) { return d->data; }
+void* deno_get_data(Deno* d) { return d->user_data; }
 
 const char* deno_v8_version() { return v8::V8::GetVersion(); }
 
diff --git a/libdeno/deno.h b/libdeno/deno.h
index b0248b7adb..d3c2cf7629 100644
--- a/libdeno/deno.h
+++ b/libdeno/deno.h
@@ -30,10 +30,10 @@ void deno_init();
 const char* deno_v8_version();
 void deno_set_v8_flags(int* argc, char** argv);
 
-Deno* deno_new(void* data, deno_recv_cb cb);
+Deno* deno_new(void* user_data, deno_recv_cb cb);
 void deno_delete(Deno* d);
 
-// Returns the void* data provided in deno_new.
+// Returns the void* user_data provided in deno_new.
 void* deno_get_data(Deno*);
 
 // Returns false on error.
diff --git a/libdeno/from_filesystem.cc b/libdeno/from_filesystem.cc
index 0852f1558b..701925c9c1 100644
--- a/libdeno/from_filesystem.cc
+++ b/libdeno/from_filesystem.cc
@@ -14,7 +14,7 @@
 
 namespace deno {
 
-Deno* NewFromFileSystem(void* data, deno_recv_cb cb) {
+Deno* NewFromFileSystem(void* user_data, deno_recv_cb cb) {
   std::string exe_path;
   CHECK(deno::ExePath(&exe_path));
   std::string exe_dir = deno::Dirname(exe_path);  // Always ends with a slash.
@@ -30,7 +30,7 @@ Deno* NewFromFileSystem(void* data, deno_recv_cb cb) {
   Deno* d = new Deno;
   d->currentArgs = nullptr;
   d->cb = cb;
-  d->data = data;
+  d->user_data = user_data;
   v8::Isolate::CreateParams params;
   params.array_buffer_allocator =
       v8::ArrayBuffer::Allocator::NewDefaultAllocator();
@@ -55,7 +55,7 @@ Deno* NewFromFileSystem(void* data, deno_recv_cb cb) {
 }  // namespace deno
 
 extern "C" {
-Deno* deno_new(void* data, deno_recv_cb cb) {
-  return deno::NewFromFileSystem(data, cb);
+Deno* deno_new(void* user_data, deno_recv_cb cb) {
+  return deno::NewFromFileSystem(user_data, cb);
 }
 }
diff --git a/libdeno/from_snapshot.cc b/libdeno/from_snapshot.cc
index bcd215f820..b204af08b7 100644
--- a/libdeno/from_snapshot.cc
+++ b/libdeno/from_snapshot.cc
@@ -43,11 +43,11 @@ void DeserializeInternalFields(v8::Local<v8::Object> holder, int index,
   deserialized_data.push_back(embedder_field);
 }
 
-Deno* NewFromSnapshot(void* data, deno_recv_cb cb) {
+Deno* NewFromSnapshot(void* user_data, deno_recv_cb cb) {
   Deno* d = new Deno;
   d->currentArgs = nullptr;
   d->cb = cb;
-  d->data = data;
+  d->user_data = user_data;
   v8::Isolate::CreateParams params;
   params.array_buffer_allocator =
       v8::ArrayBuffer::Allocator::NewDefaultAllocator();
@@ -80,7 +80,7 @@ Deno* NewFromSnapshot(void* data, deno_recv_cb cb) {
 }  // namespace deno
 
 extern "C" {
-Deno* deno_new(void* data, deno_recv_cb cb) {
-  return deno::NewFromSnapshot(data, cb);
+Deno* deno_new(void* user_data, deno_recv_cb cb) {
+  return deno::NewFromSnapshot(user_data, cb);
 }
 }
diff --git a/libdeno/internal.h b/libdeno/internal.h
index dd377b36c5..08e5cc0f59 100644
--- a/libdeno/internal.h
+++ b/libdeno/internal.h
@@ -18,7 +18,7 @@ struct deno_s {
   v8::Persistent<v8::Map> async_data_map;
   deno_recv_cb cb;
   int32_t next_req_id;
-  void* data;
+  void* user_data;
 };
 }
 
@@ -37,7 +37,7 @@ static intptr_t external_references[] = {
     reinterpret_cast<intptr_t>(Send),
     reinterpret_cast<intptr_t>(SetGlobalErrorHandler), 0};
 
-Deno* NewFromSnapshot(void* data, deno_recv_cb cb);
+Deno* NewFromSnapshot(void* user_data, deno_recv_cb cb);
 
 void InitializeContext(v8::Isolate* isolate, v8::Local<v8::Context> context,
                        const char* js_filename, const std::string& js_source,
diff --git a/src/isolate.rs b/src/isolate.rs
index bc7faafa67..c8e962f342 100644
--- a/src/isolate.rs
+++ b/src/isolate.rs
@@ -102,10 +102,7 @@ impl Isolate {
     });
 
     (*isolate).libdeno_isolate = unsafe {
-      libdeno::deno_new(
-        isolate.as_ref() as *const _ as *const c_void,
-        pre_dispatch,
-      )
+      libdeno::deno_new(isolate.as_mut() as *mut _ as *mut c_void, pre_dispatch)
     };
 
     isolate
diff --git a/src/libdeno.rs b/src/libdeno.rs
index c7a03e3bb2..b48ddd1663 100644
--- a/src/libdeno.rs
+++ b/src/libdeno.rs
@@ -30,10 +30,10 @@ extern "C" {
   pub fn deno_init();
   pub fn deno_v8_version() -> *const c_char;
   pub fn deno_set_v8_flags(argc: *mut c_int, argv: *mut *mut c_char);
-  pub fn deno_new(data: *const c_void, cb: DenoRecvCb) -> *const isolate;
+  pub fn deno_new(user_data: *mut c_void, cb: DenoRecvCb) -> *const isolate;
   pub fn deno_delete(i: *const isolate);
   pub fn deno_last_exception(i: *const isolate) -> *const c_char;
-  pub fn deno_get_data(i: *const isolate) -> *const c_void;
+  pub fn deno_get_data(i: *const isolate) -> *mut c_void;
   pub fn deno_respond(i: *const isolate, req_id: i32, buf: deno_buf);
   pub fn deno_execute(
     i: *const isolate,