Index: /trunk/src/VBox/Devices/Audio/DrvHostALSAAudio.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/DrvHostALSAAudio.cpp	(revision 56648)
+++ /trunk/src/VBox/Devices/Audio/DrvHostALSAAudio.cpp	(revision 56649)
@@ -824,6 +824,6 @@
      */
     Assert(cAvail);
-    size_t cbToRead = RT_MIN(AUDIOMIXBUF_S2B(&pHstStrmIn->MixBuf, cAvail),
-                             AudioMixBufFreeBytes(&pHstStrmIn->MixBuf));
+    size_t cbMixFree = AudioMixBufFreeBytes(&pHstStrmIn->MixBuf);
+    size_t cbToRead = RT_MIN((size_t)AUDIOMIXBUF_S2B(&pHstStrmIn->MixBuf, cAvail), cbMixFree);
 
     LogFlowFunc(("cbToRead=%zu, cAvail=%RI32\n", cbToRead, cAvail));
Index: /trunk/src/VBox/Devices/Audio/DrvHostCoreAudio.cpp
===================================================================
--- /trunk/src/VBox/Devices/Audio/DrvHostCoreAudio.cpp	(revision 56648)
+++ /trunk/src/VBox/Devices/Audio/DrvHostCoreAudio.cpp	(revision 56649)
@@ -1507,5 +1507,6 @@
     do
     {
-        size_t cbBuf = RT_MIN(AudioMixBufSizeBytes(&pHstStrmOut->MixBuf), pStreamOut->cbPCMBuf);
+        size_t cbMixBuf = AudioMixBufSizeBytes(&pHstStrmOut->MixBuf);
+        size_t cbBuf    = RT_MIN(cbMixBuf, pStreamOut->cbPCMBuf);
         size_t cbToRead = RT_MIN(cbBuf, RTCircBufFree(pStreamOut->pBuf));
         LogFlowFunc(("cbToRead=%zu\n", cbToRead));