diff --git a/dll/win32/winmm/mmio.c b/dll/win32/winmm/mmio.c
index 5e86722e747..9182d3b800c 100644
--- a/dll/win32/winmm/mmio.c
+++ b/dll/win32/winmm/mmio.c
@@ -1161,7 +1161,7 @@ MMRESULT WINAPI mmioDescend(HMMIO hmmio, LPMMCKINFO lpck,
         LONG ix;
 
         ix = mmioRead(hmmio, (LPSTR)lpck, 3 * sizeof(DWORD));
-        if (ix < 2*sizeof(DWORD))
+        if (ix < 0 || ix < 2*sizeof(DWORD))
         {
             mmioSeek(hmmio, dwOldPos, SEEK_SET);
             WARN("return ChunkNotFound\n");
@@ -1263,7 +1263,7 @@ MMRESULT WINAPI mmioCreateChunk(HMMIO hmmio, MMCKINFO* lpck, UINT uFlags)
 
     ix = mmioWrite(hmmio, (LPSTR)lpck, size);
     TRACE("after mmioWrite ix = %d req = %d, errno = %d\n", ix, size, errno);
-    if (ix < size) {
+    if (ix != size) {
 	mmioSeek(hmmio, dwOldPos, SEEK_SET);
 	WARN("return CannotWrite\n");
 	return MMIOERR_CANNOTWRITE;
diff --git a/dll/win32/winmm/playsound.c b/dll/win32/winmm/playsound.c
index f71cbd32a21..b599073a2db 100644
--- a/dll/win32/winmm/playsound.c
+++ b/dll/win32/winmm/playsound.c
@@ -428,6 +428,7 @@ static BOOL proc_PlaySound(WINE_PLAYSOUND *wps)
     LPWAVEHDR		waveHdr = NULL;
     INT			count, bufsize, left, index;
     struct playsound_data	s;
+    LONG                r;
 
     s.hEvent = 0;
 
@@ -451,8 +452,9 @@ static BOOL proc_PlaySound(WINE_PLAYSOUND *wps)
     lpWaveFormat = HeapAlloc(GetProcessHeap(), 0, mmckInfo.cksize);
     if (!lpWaveFormat)
         goto errCleanUp;
-    if (mmioRead(wps->hmmio, (HPSTR)lpWaveFormat, mmckInfo.cksize) < sizeof(PCMWAVEFORMAT))
-	goto errCleanUp;
+    r = mmioRead(wps->hmmio, (HPSTR)lpWaveFormat, mmckInfo.cksize);
+    if (r < 0 || r < sizeof(PCMWAVEFORMAT))
+	    goto errCleanUp;
 
     TRACE("wFormatTag=%04X !\n", 	lpWaveFormat->wFormatTag);
     TRACE("nChannels=%d\n", 		lpWaveFormat->nChannels);