diff --git a/src/corelib/global/qcompare.h b/src/corelib/global/qcompare.h
index fadd10f422..4bc97fa24e 100644
--- a/src/corelib/global/qcompare.h
+++ b/src/corelib/global/qcompare.h
@@ -154,7 +154,7 @@ private:
 
     // instead of the exposition only is_ordered member in [cmp.partialord],
     // use a private function
-    constexpr bool isOrdered() noexcept
+    constexpr bool isOrdered() const noexcept
     { return m_order != static_cast<QtPrivate::CompareUnderlyingType>(QtPrivate::Uncomparable::Unordered); }
 
     QtPrivate::CompareUnderlyingType m_order;