diff --git a/runtime/src/main/cpp/Weak.cpp b/runtime/src/main/cpp/Weak.cpp
index 4c5d679249c..df2f0e490f5 100644
--- a/runtime/src/main/cpp/Weak.cpp
+++ b/runtime/src/main/cpp/Weak.cpp
@@ -29,12 +29,10 @@ inline WeakReferenceCounter* asWeakReferenceCounter(ObjHeader* obj) {
   return reinterpret_cast<WeakReferenceCounter*>(obj);
 }
 
-constexpr int referredOffset = 0;
-constexpr int lockOffset = sizeof(void*);
-
 #if !KONAN_NO_THREADS
 
 inline void lock(int32_t* address) {
+    RuntimeAssert(*address == 0 || *address == 1, "Incorrect lock state");
     while (__sync_val_compare_and_swap(address, 0, 1) == 1);
 }
 
diff --git a/runtime/src/main/kotlin/kotlin/native/concurrent/Worker.kt b/runtime/src/main/kotlin/kotlin/native/concurrent/Worker.kt
index fdc28fec892..9c26470e7bb 100644
--- a/runtime/src/main/kotlin/kotlin/native/concurrent/Worker.kt
+++ b/runtime/src/main/kotlin/kotlin/native/concurrent/Worker.kt
@@ -47,6 +47,14 @@ public inline class Worker @PublishedApi internal constructor(val id: Int) {
             val id = currentInternal()
             return if (id != 0) Worker(id) else null
         }
+
+        /**
+         * Create worker object from a C pointer.
+         *
+         *  @param pointer value returned earlier by [Worker.asCPointer]
+         */
+        public fun fromCPointer(pointer: COpaquePointer?) =
+                if (pointer != null) Worker(pointer.toLong().toInt()) else throw IllegalArgumentException()
     }
 
     /**
@@ -81,4 +89,10 @@ public inline class Worker @PublishedApi internal constructor(val id: Int) {
             throw RuntimeException("Shall not be called directly")
 
     override public fun toString(): String = "worker $id"
+
+    /**
+     * Convert worker to a COpaquePointer value that could be passed via native void* pointer.
+     * Can be used as an argument of [Worker.fromCPointer].
+     */
+    public fun asCPointer() : COpaquePointer? = id.toLong().toCPointer()
 }
\ No newline at end of file
diff --git a/samples/videoplayer/src/videoPlayerMain/kotlin/SDLAudio.kt b/samples/videoplayer/src/videoPlayerMain/kotlin/SDLAudio.kt
index f402dfb407b..b15358d8dcc 100644
--- a/samples/videoplayer/src/videoPlayerMain/kotlin/SDLAudio.kt
+++ b/samples/videoplayer/src/videoPlayerMain/kotlin/SDLAudio.kt
@@ -24,7 +24,6 @@ private fun SampleFormat.toSDLFormat(): SDL_AudioFormat? = when (this) {
 }
 
 class SDLAudio(val player: VideoPlayer) : DisposableContainer() {
-    private val workerStable = StableRef.create(player.worker)
     private var state = State.STOPPED
 
     fun start(audio: AudioOutput) {
@@ -40,7 +39,7 @@ class SDLAudio(val player: VideoPlayer) : DisposableContainer() {
                 channels = audio.channels.convert()
                 silence = 0u
                 samples = 4096u
-                userdata = workerStable.asCPointer()
+                userdata = player.worker.asCPointer()
                 callback = staticCFunction(::audioCallback)
             }
             val realSpec = alloc<SDL_AudioSpec>()
@@ -63,7 +62,6 @@ class SDLAudio(val player: VideoPlayer) : DisposableContainer() {
     fun stop() {
         pause()
         state = state.transition(State.PAUSED, State.STOPPED) { SDL_CloseAudio() }
-        workerStable.dispose()
     }
 }
 
@@ -75,7 +73,7 @@ private fun audioCallback(userdata: COpaquePointer?, buffer: CPointer<Uint8Var>?
     // This handler will be invoked in the audio thread, so reinit runtime.
     kotlin.native.initRuntimeIfNeeded()
     val decoder = decoder ?:
-        DecoderWorker(userdata!!.asStableRef<Worker>().get()).also { decoder = it }
+        DecoderWorker(Worker.fromCPointer(userdata)).also { decoder = it }
     var outPosition = 0
     while (outPosition < length) {
         val frame = decoder.nextAudioFrame(length - outPosition)