diff --git a/src/testlib/qtestcase.h b/src/testlib/qtestcase.h
index 2c2c3263ff6..b118a2066b9 100644
--- a/src/testlib/qtestcase.h
+++ b/src/testlib/qtestcase.h
@@ -315,8 +315,9 @@ namespace QTest
     Q_TESTLIB_EXPORT void maybeThrowOnFail();
     Q_TESTLIB_EXPORT void maybeThrowOnSkip();
 
+    Q_DECL_COLD_FUNCTION
     Q_TESTLIB_EXPORT QString formatTryTimeoutDebugMessage(q_no_char8_t::QUtf8StringView expr, int timeout, int actual);
-    Q_TESTLIB_EXPORT
+    Q_TESTLIB_EXPORT Q_DECL_COLD_FUNCTION
     const char *formatPropertyTestHelperFailure(char *msg, size_t maxMsgLen,
                                                 const char *actual, const char *expected,
                                                 const char *actualExpr,
diff --git a/src/testlib/qtestresult.cpp b/src/testlib/qtestresult.cpp
index 0e1c9d7ad95..a49cdbadc44 100644
--- a/src/testlib/qtestresult.cpp
+++ b/src/testlib/qtestresult.cpp
@@ -342,6 +342,7 @@ static int approx_wide_len(const char *s)
 }
 
 // Overload to format failures for "const char *" - no need to strdup().
+static Q_DECL_COLD_FUNCTION
 void formatFailMessage(char *msg, size_t maxMsgLen,
                        const char *failureMsg,
                        const char *val1, const char *val2,
@@ -380,6 +381,7 @@ QTest::Internal::formatPropertyTestHelperFailure(char *msg, size_t maxMsgLen,
 
 // Format failures using the toString() template
 template <class Actual, class Expected>
+static Q_DECL_COLD_FUNCTION
 void formatFailMessage(char *msg, size_t maxMsgLen,
                        const char *failureMsg,
                        const Actual &val1, const Expected &val2,