diff --git a/Help/command/file.rst b/Help/command/file.rst
index 3e669c24dc1dff794a4c66d3f411bf9878c38b1b..b2e4eea4443d6cf40df3be882399b47bf5a990a0 100644
--- a/Help/command/file.rst
+++ b/Help/command/file.rst
@@ -304,6 +304,11 @@ Exactly one ``CONTENT`` or ``INPUT`` option must be given.  A specific
 Generated files are modified on subsequent cmake runs only if their content
 is changed.
 
+Note also that ``file(GENERATE)`` does not create the output file until the
+generation phase. The output file will not yet have been written when the
+``file(GENERATE)`` command returns, it is written only after processing all
+of a project's ``CMakeLists.txt`` files.
+
 ------------------------------------------------------------------------------
 
 ::