diff --git a/src/corelib/text/qstringconverter_p.h b/src/corelib/text/qstringconverter_p.h
index b5d3d53bb81..7533e094a9d 100644
--- a/src/corelib/text/qstringconverter_p.h
+++ b/src/corelib/text/qstringconverter_p.h
@@ -44,7 +44,7 @@ struct QUtf8BaseTraits
     static uchar peekByte(const uchar *ptr, qsizetype n = 0)
     { return ptr[n]; }
 
-    static uchar peekByte(const char8_t *ptr, int n = 0)
+    static uchar peekByte(const char8_t *ptr, qsizetype n = 0)
     { return ptr[n]; }
 
     static qptrdiff availableBytes(const uchar *ptr, const uchar *end)
@@ -56,7 +56,7 @@ struct QUtf8BaseTraits
     static void advanceByte(const uchar *&ptr, qsizetype n = 1)
     { ptr += n; }
 
-    static void advanceByte(const char8_t *&ptr, int n = 1)
+    static void advanceByte(const char8_t *&ptr, qsizetype n = 1)
     { ptr += n; }
 
     static void appendUtf16(char16_t *&ptr, char16_t uc)