diff --git a/dlls/wineoss.drv/midi.c b/dlls/wineoss.drv/midi.c
index 3a2ab2580d6..24b3e7037b0 100644
--- a/dlls/wineoss.drv/midi.c
+++ b/dlls/wineoss.drv/midi.c
@@ -230,9 +230,8 @@ static LRESULT OSS_MidiInit(void)
             MidiOutDev[i].caps.wTechnology = MOD_MIDIPORT;
             MidiOutDev[i].bEnabled = FALSE;
 	} else {
-            MultiByteToWideChar( CP_UNIXCP, 0, sinfo.name, -1,
-                                 MidiOutDev[i].caps.szPname,
-                                 sizeof(MidiOutDev[i].caps.szPname)/sizeof(WCHAR) );
+            MultiByteToWideChar(CP_UNIXCP, 0, sinfo.name, -1, MidiOutDev[i].caps.szPname,
+                                ARRAY_SIZE(MidiOutDev[i].caps.szPname));
             MidiOutDev[i].caps.wTechnology = MIDI_UnixToWindowsDeviceType(sinfo.synth_type);
 
             if (MOD_MIDIPORT != MidiOutDev[i].caps.wTechnology) {
@@ -313,7 +312,7 @@ static LRESULT OSS_MidiInit(void)
         } else {
             MultiByteToWideChar(CP_UNIXCP, 0, minfo.name, -1,
                                 MidiOutDev[numsynthdevs + i].caps.szPname,
-                                sizeof(MidiOutDev[numsynthdevs + i].caps.szPname) / sizeof(WCHAR));
+                                ARRAY_SIZE(MidiOutDev[numsynthdevs + i].caps.szPname));
             MidiOutDev[numsynthdevs + i].bEnabled = TRUE;
         }
 	MidiOutDev[numsynthdevs + i].caps.wTechnology = MOD_MIDIPORT;
@@ -338,9 +337,8 @@ static LRESULT OSS_MidiInit(void)
             wsprintfW(MidiInDev[i].caps.szPname, fmt, numsynthdevs + i);
             MidiInDev[i].state = -1;
         } else {
-            MultiByteToWideChar(CP_UNIXCP, 0, minfo.name, -1,
-                                MidiInDev[i].caps.szPname,
-                                sizeof(MidiInDev[i].caps.szPname) / sizeof(WCHAR));
+            MultiByteToWideChar(CP_UNIXCP, 0, minfo.name, -1, MidiInDev[i].caps.szPname,
+                                ARRAY_SIZE(MidiInDev[i].caps.szPname));
             MidiInDev[i].state = 0;
         }
 	MidiInDev[i].caps.dwSupport   = 0; /* mandatory with MIDIINCAPS */
diff --git a/dlls/wineoss.drv/mmdevdrv.c b/dlls/wineoss.drv/mmdevdrv.c
index 1686c8c96c1..fa3f885ea1a 100644
--- a/dlls/wineoss.drv/mmdevdrv.c
+++ b/dlls/wineoss.drv/mmdevdrv.c
@@ -349,8 +349,7 @@ static void get_device_guid(EDataFlow flow, const char *device, GUID *guid)
     else
         key_name[0] = '0';
     key_name[1] = ',';
-    MultiByteToWideChar(CP_UNIXCP, 0, device, -1, key_name + 2,
-            (sizeof(key_name) / sizeof(*key_name)) - 2);
+    MultiByteToWideChar(CP_UNIXCP, 0, device, -1, key_name + 2, ARRAY_SIZE(key_name) - 2);
 
     if(RegOpenKeyExW(HKEY_CURRENT_USER, drv_key_devicesW, 0, KEY_WRITE|KEY_READ, &key) == ERROR_SUCCESS){
         if(RegOpenKeyExW(key, key_name, 0, KEY_READ, &dev_key) == ERROR_SUCCESS){
@@ -543,11 +542,11 @@ HRESULT WINAPI AUDDRV_GetEndpointIDs(EDataFlow flow, WCHAR ***ids, GUID **guids,
             len = MultiByteToWideChar(CP_UNIXCP, 0, ai.name, -1, NULL, 0);
             if(flow == eRender){
                 prefix = outW;
-                prefix_len = (sizeof(outW) / sizeof(*outW)) - 1;
+                prefix_len = ARRAY_SIZE(outW) - 1;
                 len += prefix_len;
             }else{
                 prefix = inW;
-                prefix_len = (sizeof(inW) / sizeof(*inW)) - 1;
+                prefix_len = ARRAY_SIZE(inW) - 1;
                 len += prefix_len;
             }
             (*ids)[*num] = HeapAlloc(GetProcessHeap(), 0,