diff --git a/src/widgets/util/qundostack.cpp b/src/widgets/util/qundostack.cpp
index 5bcfa57b3774077fc5918110851851cd1c13b9bd..bd41fb60c12081f21bc57f30f687ca31e32f24f9 100644
--- a/src/widgets/util/qundostack.cpp
+++ b/src/widgets/util/qundostack.cpp
@@ -623,6 +623,8 @@ void QUndoStack::push(QUndoCommand *cmd)
     Marks the stack as clean and emits cleanChanged() if the stack was
     not already clean.
 
+    This is typically called when a document is saved, for example.
+
     Whenever the stack returns to this state through the use of undo/redo
     commands, it emits the signal cleanChanged(). This signal is also
     emitted when the stack leaves the clean state.