diff --git a/kotlinx-coroutines-core/common/src/Builders.common.kt b/kotlinx-coroutines-core/common/src/Builders.common.kt
index 64bff500dc..606e9a4bdf 100644
--- a/kotlinx-coroutines-core/common/src/Builders.common.kt
+++ b/kotlinx-coroutines-core/common/src/Builders.common.kt
@@ -108,9 +108,11 @@ private class LazyDeferredCoroutine<T>(
     parentContext: CoroutineContext,
     block: suspend CoroutineScope.() -> T
 ) : DeferredCoroutine<T>(parentContext, active = false) {
-    private val continuation = block.createCoroutineUnintercepted(this, this)
+    private var continuation: Continuation<Unit>? = block.createCoroutineUnintercepted(this, this)
 
     override fun onStart() {
+        val continuation = checkNotNull(this.continuation) { "Already started" }
+        this.continuation = null
         continuation.startCoroutineCancellable(this)
     }
 }
@@ -195,9 +197,11 @@ private class LazyStandaloneCoroutine(
     parentContext: CoroutineContext,
     block: suspend CoroutineScope.() -> Unit
 ) : StandaloneCoroutine(parentContext, active = false) {
-    private val continuation = block.createCoroutineUnintercepted(this, this)
+    private var continuation: Continuation<Unit>? = block.createCoroutineUnintercepted(this, this)
 
     override fun onStart() {
+        val continuation = checkNotNull(this.continuation) { "Already started" }
+        this.continuation = null
         continuation.startCoroutineCancellable(this)
     }
 }