diff --git a/src/LevelMutex.cpp b/src/LevelMutex.cpp
index 7e68057..8dc6d70 100644
--- a/src/LevelMutex.cpp
+++ b/src/LevelMutex.cpp
@@ -670,6 +670,14 @@ bool LevelMutexInfo::IsLockedByCurrentThreadImpl( void ) const
 // ----------------------------------------------------------------------------
 
 bool LevelMutexInfo::IsNotLockedByCurrentThread( void ) const volatile
+{
+	const LevelMutexInfo * pThis = const_cast< const LevelMutexInfo * >( this );
+	return pThis->IsNotLockedByCurrentThread();
+}
+
+// ----------------------------------------------------------------------------
+
+bool LevelMutexInfo::IsNotLockedByCurrentThread( void ) const
 {
     if ( !IsLocked() )
         return true;