diff --git a/src/corelib/io/qdebug.h b/src/corelib/io/qdebug.h
index a730e2f7d1c..3cd8384e3d4 100644
--- a/src/corelib/io/qdebug.h
+++ b/src/corelib/io/qdebug.h
@@ -302,7 +302,7 @@ inline QDebugIfHasDebugStream<T> operator<<(QDebug debug, const QContiguousCache
 {
     const QDebugStateSaver saver(debug);
     debug.nospace() << "QContiguousCache(";
-    for (int i = cache.firstIndex(); i <= cache.lastIndex(); ++i) {
+    for (qsizetype i = cache.firstIndex(); i <= cache.lastIndex(); ++i) {
         debug << cache[i];
         if (i != cache.lastIndex())
             debug << ", ";