diff --git a/cmake/catkin_package.cmake b/cmake/catkin_package.cmake
index 7d56edfa8..8ef6c48a9 100644
--- a/cmake/catkin_package.cmake
+++ b/cmake/catkin_package.cmake
@@ -36,8 +36,10 @@
 # :param CFG_EXTRAS: a CMake file containing extra stuff that should
 #   be accessible to users of this package after
 #   ``find_package``\ -ing it.  This file must live in the
-#   subdirectory ``cmake`` or be an absolute path.  Various additional
-#   file extension are possible:
+#   subdirectory ``cmake`` or be an absolute path.
+#   All passed extra files must have unique basenames since they are
+#   being installed into a single folder.
+#   Various additional file extension are possible:
 #   for a plain cmake file just ``.cmake``, for files expanded using
 #   CMake's ``configure_file()`` use ``.cmake.in`` or for files expanded
 #   by empy use ``.cmake.em``.  The templates can distinguish between