diff --git a/kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/CancellableContinuation.kt b/kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/CancellableContinuation.kt
index 4daf5f1..1b1adad 100644
--- a/kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/CancellableContinuation.kt
+++ b/kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/CancellableContinuation.kt
@@ -22,13 +22,16 @@
     val isCancelled: Boolean
 
     /**
-     * Tries to resume this continuation with a given value and returns `true` if it was successful,
-     * or `false` otherwise (it was already resumed or cancelled).
-     *
-     * An optional [onSuccess] callback is invoked with [value] as its parameter after the state of this continuation
-     * is updated (so that is cannot be cancelled anymore), but before it is actually resumed.
+     * Tries to resume this continuation with a given value and returns non-null object token if it was successful,
+     * or `null` otherwise (it was already resumed or cancelled). When non-null object was returned,
+     * [completeResume] must be invoked with it.
      */
-    fun tryResume(value: T, onSuccess: ((Any?) -> Unit)? = null): Boolean
+    fun tryResume(value: T): Any?
+
+    /**
+     * Completes the execution of [tryResume] on its non-null result.
+     */
+    fun completeResume(token: Any)
 
     /**
      * Makes this continuation cancellable. Use it with `holdCancellability` optional parameter to
@@ -104,16 +107,20 @@
     override val isCancelled: Boolean
         get() = getState() is Cancelled
 
-    override fun tryResume(value: T, onSuccess: ((Any?) -> Unit)?): Boolean {
+    override fun tryResume(value: T): Any? {
         while (true) { // lock-free loop on state
             val state = getState() // atomic read
             when (state) {
-                is Active -> if (updateState(state, value, onSuccess)) return true
-                else -> return false // cannot resume -- not active anymore
+                is Active -> if (tryUpdateState(state, value)) return state
+                else -> return null // cannot resume -- not active anymore
             }
         }
     }
 
+    override fun completeResume(token: Any) {
+        completeUpdateState(token, getState())
+    }
+
     @Suppress("UNCHECKED_CAST")
     override fun afterCompletion(state: Any?) {
         val decision = this.decision // volatile read