diff --git a/dlls/l3codeca.acm/mpegl3.c b/dlls/l3codeca.acm/mpegl3.c
index f71aac307f7..8ad6ae83dcb 100644
--- a/dlls/l3codeca.acm/mpegl3.c
+++ b/dlls/l3codeca.acm/mpegl3.c
@@ -676,13 +676,13 @@ static	LRESULT MPEG3_DriverDetails(PACMDRIVERDETAILSW add)
     add->cFilterTags = 0;
     add->hicon = NULL;
     MultiByteToWideChar( CP_ACP, 0, "MPEG Layer-3 Codec", -1,
-                         add->szShortName, sizeof(add->szShortName)/sizeof(WCHAR) );
+                         add->szShortName, ARRAY_SIZE( add->szShortName ));
     MultiByteToWideChar( CP_ACP, 0, "Wine MPEG3 decoder", -1,
-                         add->szLongName, sizeof(add->szLongName)/sizeof(WCHAR) );
+                         add->szLongName, ARRAY_SIZE( add->szLongName ));
     MultiByteToWideChar( CP_ACP, 0, "Brought to you by the Wine team...", -1,
-                         add->szCopyright, sizeof(add->szCopyright)/sizeof(WCHAR) );
+                         add->szCopyright, ARRAY_SIZE( add->szCopyright ));
     MultiByteToWideChar( CP_ACP, 0, "Refer to LICENSE file", -1,
-                         add->szLicensing, sizeof(add->szLicensing)/sizeof(WCHAR) );
+                         add->szLicensing, ARRAY_SIZE( add->szLicensing ));
     add->szFeatures[0] = 0;
 
     return MMSYSERR_NOERROR;