diff --git a/source/SoundCore.cpp b/source/SoundCore.cpp
index 4edbb414..4663c063 100644
--- a/source/SoundCore.cpp
+++ b/source/SoundCore.cpp
@@ -646,7 +646,8 @@ void SoundCore_SetErrorMax(const int nErrorMax)
 
 //=============================================================================
 
-static DWORD g_dwAdviseToken;
+// Use DWORD_PTR according to IReferenceClock from <strmif.h>.
+static DWORD_PTR g_pdwAdviseCookie = 0; // Not really used as pointer.
 static IReferenceClock *g_pRefClock = NULL;
 static HANDLE g_hSemaphore = NULL;
 static bool g_bRefClockTimerActive = false;
@@ -713,7 +714,9 @@ void SysClk_StartTimerUsec(DWORD dwUsecPeriod)
 		return;
 	}
 
-	if (g_pRefClock->AdvisePeriodic(rtNow, rtPeriod, g_hSemaphore, &g_dwAdviseToken) != S_OK)
+	// IReferenceClock from <strmif.h> (origin <axcore.idl>) is "oddly" defined to use HSEMAPHORE.
+	static_assert(sizeof(HSEMAPHORE) == sizeof(HANDLE), "must be same size");
+	if (g_pRefClock->AdvisePeriodic(rtNow, rtPeriod, (HSEMAPHORE)g_hSemaphore, &g_pdwAdviseCookie) != S_OK)
 	{
 		fprintf(stderr, "Error creating timer\n");
 		_ASSERT(0);
@@ -729,7 +732,7 @@ void SysClk_StopTimer()
 	if(!g_bRefClockTimerActive)
 		return;
 
-	if (g_pRefClock->Unadvise(g_dwAdviseToken) != S_OK)
+	if (g_pRefClock->Unadvise(g_pdwAdviseCookie) != S_OK)
 	{
 		fprintf(stderr, "Error deleting timer\n");
 		_ASSERT(0);
@@ -737,4 +740,4 @@ void SysClk_StopTimer()
 	}
 
 	g_bRefClockTimerActive = false;
-}
\ No newline at end of file
+}
diff --git a/source/StdAfx.h b/source/StdAfx.h
index 50fa17e3..ff8151a6 100644
--- a/source/StdAfx.h
+++ b/source/StdAfx.h
@@ -3,6 +3,11 @@
 #include <tchar.h>
 
 #include <crtdbg.h>
+// <strmif.h> has the correct IReferenceClock definition that works for both x86 and x64,
+// whereas the alternative definition in <dsound.h> is incorrect for x64. (out of
+// maintenance perhaps)
+// <strmif.h> *must* be included before <dsound.h> for x64 to work.
+#include <strmif.h>
 #include <dsound.h>
 #include <dshow.h>