diff --git a/clang/docs/ThreadSafetyAnalysis.rst b/clang/docs/ThreadSafetyAnalysis.rst
index 0a1b8049e465..19ec2352ff2b 100644
--- a/clang/docs/ThreadSafetyAnalysis.rst
+++ b/clang/docs/ThreadSafetyAnalysis.rst
@@ -857,6 +857,9 @@ implementation.
 
     // Assert that is mutex is currently held for read operations.
     void AssertReaderHeld() ASSERT_SHARED_CAPABILITY(this);
+    
+    // For negative capabilities.
+    const Mutex& operator!() const { return *this; }
   };