diff --git a/src/network/access/http2/hpacktable.cpp b/src/network/access/http2/hpacktable.cpp
index 0b69ee86a9..f20ec92d4c 100644
--- a/src/network/access/http2/hpacktable.cpp
+++ b/src/network/access/http2/hpacktable.cpp
@@ -26,8 +26,10 @@ HeaderSize entry_size(QByteArrayView name, QByteArrayView value)
     // for counting the number of references to the name and value would have
     // 32 octets of overhead."

-    const unsigned sum = unsigned(name.size() + value.size());
-    if (std::numeric_limits<unsigned>::max() - 32 < sum)
+    size_t sum;
+    if (qAddOverflow(size_t(name.size()), size_t(value.size()), &sum))
+        return HeaderSize();
+    if (sum > (std::numeric_limits<unsigned>::max() - 32))
         return HeaderSize();
     return HeaderSize(true, quint32(sum + 32));
 }