diff --git a/doc/cabal-project-description-file.rst b/doc/cabal-project-description-file.rst
index e4bd6264480..a2372b6864a 100644
--- a/doc/cabal-project-description-file.rst
+++ b/doc/cabal-project-description-file.rst
@@ -36,6 +36,8 @@ options):
 
 Any call to ``cabal build`` will consider ``cabal.project*`` files from parent
 directories when there is none in the current directory.
+If found, the ``cabal.project`` file determines the project root and
+other ``cabal.project.*`` files are read from this location only.
 
 .. _conditionals and imports: