Index: /trunk/src/VBox/Devices/Audio/AudioMixer.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/AudioMixer.cpp	(revision 87272)
+++ /trunk/src/VBox/Devices/Audio/AudioMixer.cpp	(revision 87273)
@@ -1712,5 +1712,5 @@
     {
         uint32_t cfChunk;
-        rc  = AudioMixBufAcquireReadBlock(&pSink->MixBuf, pSink->pabScratchBuf, RT_MIN(cbToWriteToStreams, pSink->cbScratchBuf),
+        rc  = AudioMixBufAcquireReadBlock(&pSink->MixBuf, pSink->pabScratchBuf, RT_MIN(cbToWriteToStreams, (uint32_t)pSink->cbScratchBuf),
                                           &cfChunk);
         if (RT_FAILURE(rc))