diff --git a/reactive/kotlinx-coroutines-reactive/src/Publish.kt b/reactive/kotlinx-coroutines-reactive/src/Publish.kt
index a5bc980a94..df61e04943 100644
--- a/reactive/kotlinx-coroutines-reactive/src/Publish.kt
+++ b/reactive/kotlinx-coroutines-reactive/src/Publish.kt
@@ -80,7 +80,6 @@ public class PublisherCoroutine<in T>(
     override fun invokeOnClose(handler: (Throwable?) -> Unit): Nothing =
         throw UnsupportedOperationException("PublisherCoroutine doesn't support invokeOnClose")
 
-    // TODO: will throw if `null` is passed -- is throwing this kind of programmer-induced errors okay?
     override fun trySend(element: T): ChannelResult<Unit> =
         if (!mutex.tryLock()) {
             ChannelResult.failure()
@@ -134,7 +133,7 @@ public class PublisherCoroutine<in T>(
      */
     private fun doLockedNext(elem: T): Throwable? {
         if (elem == null) {
-            throw NullPointerException("Can not emit null")
+            throw NullPointerException("Attempted to emit `null` inside a reactive publisher")
         }
         /** This guards against the case when the caller of this function managed to lock the mutex not because some
          * elements were requested--and thus it is permitted to call `onNext`--but because the channel was closed.
diff --git a/reactive/kotlinx-coroutines-rx2/src/RxCancellable.kt b/reactive/kotlinx-coroutines-rx2/src/RxCancellable.kt
index 0fe43f1cee..3e39033ed7 100644
--- a/reactive/kotlinx-coroutines-rx2/src/RxCancellable.kt
+++ b/reactive/kotlinx-coroutines-rx2/src/RxCancellable.kt
@@ -20,6 +20,7 @@ internal fun handleUndeliverableException(cause: Throwable, context: CoroutineCo
     try {
         RxJavaPlugins.onError(cause)
     } catch (e: Throwable) {
+        cause.addSuppressed(e)
         handleCoroutineException(context, cause)
     }
 }
diff --git a/reactive/kotlinx-coroutines-rx3/src/RxCancellable.kt b/reactive/kotlinx-coroutines-rx3/src/RxCancellable.kt
index 2995159850..1017b112f1 100644
--- a/reactive/kotlinx-coroutines-rx3/src/RxCancellable.kt
+++ b/reactive/kotlinx-coroutines-rx3/src/RxCancellable.kt
@@ -20,6 +20,7 @@ internal fun handleUndeliverableException(cause: Throwable, context: CoroutineCo
     try {
         RxJavaPlugins.onError(cause)
     } catch (e: Throwable) {
+        cause.addSuppressed(e)
         handleCoroutineException(context, cause)
     }
 }