diff --git a/Help/command/file.rst b/Help/command/file.rst
index 14ca20c33..869350a8f 100644
--- a/Help/command/file.rst
+++ b/Help/command/file.rst
@@ -271,6 +271,8 @@ from the input content to produce the output content.  The options are:
 
 Exactly one ``CONTENT`` or ``INPUT`` option must be given.  A specific
 ``OUTPUT`` file may be named by at most one invocation of ``file(GENERATE)``.
+Generated files are modified on subsequent cmake runs only if their content
+is changed.
 
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