diff --git a/src/corelib/text/qbytearray.cpp b/src/corelib/text/qbytearray.cpp
index f652d1c5c7..4c9282df26 100644
--- a/src/corelib/text/qbytearray.cpp
+++ b/src/corelib/text/qbytearray.cpp
@@ -2716,10 +2716,10 @@ static qsizetype lastIndexOfHelper(const char *haystack, qsizetype l, const char
 
     const char *end = haystack;
     haystack += from;
-    const auto ol_minus_1 = std::size_t(ol - 1);
+    const qregisteruint ol_minus_1 = ol - 1;
     const char *n = needle + ol_minus_1;
     const char *h = haystack + ol_minus_1;
-    std::size_t hashNeedle = 0, hashHaystack = 0;
+    qregisteruint hashNeedle = 0, hashHaystack = 0;
     qsizetype idx;
     for (idx = 0; idx < ol; ++idx) {
         hashNeedle = ((hashNeedle<<1) + *(n-idx));
@@ -2731,8 +2731,8 @@ static qsizetype lastIndexOfHelper(const char *haystack, qsizetype l, const char
         if (hashHaystack == hashNeedle && memcmp(needle, haystack, ol) == 0)
             return haystack - end;
         --haystack;
-        if (ol_minus_1 < sizeof(std::size_t) * CHAR_BIT)
-            hashHaystack -= std::size_t(*(haystack + ol)) << ol_minus_1;
+        if (ol_minus_1 < sizeof(ol_minus_1) * CHAR_BIT)
+            hashHaystack -= qregisteruint(*(haystack + ol)) << ol_minus_1;
         hashHaystack <<= 1;
     }
     return -1;
diff --git a/src/corelib/text/qbytearraymatcher.cpp b/src/corelib/text/qbytearraymatcher.cpp
index 20942e0a6c..a332f035ef 100644
--- a/src/corelib/text/qbytearraymatcher.cpp
+++ b/src/corelib/text/qbytearraymatcher.cpp
@@ -270,8 +270,8 @@ qsizetype qFindByteArray(const char *haystack0, qsizetype l, qsizetype from,
     */
     const char *haystack = haystack0 + from;
     const char *end = haystack0 + (l - sl);
-    const auto sl_minus_1 = std::size_t(sl - 1);
-    std::size_t hashNeedle = 0, hashHaystack = 0;
+    const qregisteruint sl_minus_1 = sl - 1;
+    qregisteruint hashNeedle = 0, hashHaystack = 0;
     qsizetype idx;
     for (idx = 0; idx < sl; ++idx) {
         hashNeedle = ((hashNeedle<<1) + needle[idx]);
@@ -285,8 +285,8 @@ qsizetype qFindByteArray(const char *haystack0, qsizetype l, qsizetype from,
              && memcmp(needle, haystack, sl) == 0)
             return haystack - haystack0;
 
-        if (sl_minus_1 < sizeof(std::size_t) * CHAR_BIT)
-            hashHaystack -= std::size_t(*haystack) << sl_minus_1;
+        if (sl_minus_1 < sizeof(sl_minus_1) * CHAR_BIT)
+            hashHaystack -= qregisteruint(*haystack) << sl_minus_1;
         hashHaystack <<= 1;
         ++haystack;
     }
diff --git a/src/corelib/text/qstring.cpp b/src/corelib/text/qstring.cpp
index f0bf0c50a3..d0c39e0037 100644
--- a/src/corelib/text/qstring.cpp
+++ b/src/corelib/text/qstring.cpp
@@ -63,8 +63,8 @@
 #endif
 
 #define REHASH(a) \
-    if (sl_minus_1 < sizeof(std::size_t) * CHAR_BIT)  \
-        hashHaystack -= std::size_t(a) << sl_minus_1; \
+    if (sl_minus_1 < sizeof(sl_minus_1) * CHAR_BIT)  \
+        hashHaystack -= decltype(hashHaystack)(a) << sl_minus_1; \
     hashHaystack <<= 1
 
 QT_BEGIN_NAMESPACE
@@ -183,10 +183,10 @@ static qsizetype qLastIndexOf(Haystack haystack0, qsizetype from,
     const auto needle = needle0.data();
     const auto *end = haystack;
     haystack += from;
-    const std::size_t sl_minus_1 = sl ? sl - 1 : 0;
+    const qregisteruint sl_minus_1 = sl ? sl - 1 : 0;
     const auto *n = needle + sl_minus_1;
     const auto *h = haystack + sl_minus_1;
-    std::size_t hashNeedle = 0, hashHaystack = 0;
+    qregisteruint hashNeedle = 0, hashHaystack = 0;
 
     if (cs == Qt::CaseSensitive) {
         for (qsizetype idx = 0; idx < sl; ++idx) {
@@ -9905,8 +9905,8 @@ qsizetype QtPrivate::findString(QStringView haystack0, qsizetype from, QStringVi
     const char16_t *needle = needle0.utf16();
     const char16_t *haystack = haystack0.utf16() + from;
     const char16_t *end = haystack0.utf16() + (l - sl);
-    const std::size_t sl_minus_1 = sl - 1;
-    std::size_t hashNeedle = 0, hashHaystack = 0;
+    const qregisteruint sl_minus_1 = sl - 1;
+    qregisteruint hashNeedle = 0, hashHaystack = 0;
     qsizetype idx;
 
     if (cs == Qt::CaseSensitive) {