diff --git a/src/corelib/compat/removed_api.cpp b/src/corelib/compat/removed_api.cpp
index 316c3518501..8260d50fd3a 100644
--- a/src/corelib/compat/removed_api.cpp
+++ b/src/corelib/compat/removed_api.cpp
@@ -1461,6 +1461,8 @@ QNoDebug QMessageLogger::noDebug() const noexcept
     return QNoDebug();
 }
 
+#include "qmutex.h" // removed, previously-inline API
+
 #include "qstring.h" // inlined API
 
 // #include "qotherheader.h"
diff --git a/src/corelib/thread/qmutex.h b/src/corelib/thread/qmutex.h
index 68377f3d699..a45dcee2756 100644
--- a/src/corelib/thread/qmutex.h
+++ b/src/corelib/thread/qmutex.h
@@ -88,6 +88,11 @@ private:
             return false;
         return d_ptr.testAndSetAcquire(nullptr, dummyLocked());
     }
+#if QT_CORE_REMOVED_SINCE(6, 10)
+    inline bool fastTryUnlock() noexcept {
+        return d_ptr.testAndSetRelease(dummyLocked(), nullptr);
+    }
+#endif
 
     void lockInternal() noexcept(FutexAlwaysAvailable);
     bool lockInternal(QDeadlineTimer timeout) noexcept(FutexAlwaysAvailable);