diff --git a/taglib/toolkit/tstring.h b/taglib/toolkit/tstring.h
index 5a705ada..59611ab0 100644
--- a/taglib/toolkit/tstring.h
+++ b/taglib/toolkit/tstring.h
@@ -42,7 +42,7 @@
  * conversion happening in the background
  */
 
-#if QT_VERSION >= 0x040000
+#if defined(QT_VERSION) && (QT_VERSION >= 0x040000)
 #define QStringToTString(s) TagLib::String(s.toUtf8().data(), TagLib::String::UTF8)
 #else
 #define QStringToTString(s) TagLib::String(s.utf8().data(), TagLib::String::UTF8)