diff --git a/modules/rostests/winetests/pdh/pdh.c b/modules/rostests/winetests/pdh/pdh.c
index 573bcc3a108..0a17906afbd 100644
--- a/modules/rostests/winetests/pdh/pdh.c
+++ b/modules/rostests/winetests/pdh/pdh.c
@@ -700,21 +700,21 @@ static void test_PdhLookupPerfNameByIndexW( void )
     ret = PdhLookupPerfNameByIndexW( NULL, 6, buffer, &size );
     ok(ret == PDH_MORE_DATA || ret == PDH_INSUFFICIENT_BUFFER, "PdhLookupPerfNameByIndexW failed 0x%08x\n", ret);
 
-    size = sizeof(buffer) / sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = PdhLookupPerfNameByIndexW( NULL, 6, buffer, &size );
     ok(ret == ERROR_SUCCESS, "PdhLookupPerfNameByIndexW failed 0x%08x\n", ret);
-    ok(size == sizeof(processor_time) / sizeof(WCHAR), "PdhLookupPerfNameByIndexW failed %d\n", size);
+    ok(size == ARRAY_SIZE(processor_time), "PdhLookupPerfNameByIndexW failed %d\n", size);
 
-    size = sizeof(buffer) / sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = PdhLookupPerfNameByIndexW( NULL, 674, NULL, &size );
     ok(ret == PDH_INVALID_ARGUMENT ||
        ret == PDH_MORE_DATA, /* win2k3 */
        "PdhLookupPerfNameByIndexW failed 0x%08x\n", ret);
 
-    size = sizeof(buffer) / sizeof(WCHAR);
+    size = ARRAY_SIZE(buffer);
     ret = PdhLookupPerfNameByIndexW( NULL, 674, buffer, &size );
     ok(ret == ERROR_SUCCESS, "PdhLookupPerfNameByIndexW failed 0x%08x\n", ret);
-    ok(size == sizeof(uptime) / sizeof(WCHAR), "PdhLookupPerfNameByIndexW failed %d\n", size);
+    ok(size == ARRAY_SIZE(uptime), "PdhLookupPerfNameByIndexW failed %d\n", size);
 }
 
 static void test_PdhValidatePathA( void )