diff --git a/etc/NEWS b/etc/NEWS
index 014184f1fa6..0a1c217d897 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -696,9 +696,11 @@ you can add this to your init script:
 
     (setopt project-switch-commands #'project-prefix-or-any-command)
 
+---
 *** New variable 'project-files-relative-names'.
-Project backends can support it to improve the performance of their
-'project-files' implementation when this variable is non-nil.
+If it's non-nil, 'project-files' can return file names relative to the
+project root.  Project backends can use this to improve the performance
+of their 'project-files' implementation.
 
 ** VC
 
diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
index b716d442aed..a3181340411 100644
--- a/lisp/progmodes/project.el
+++ b/lisp/progmodes/project.el
@@ -324,10 +324,11 @@ end it with `/'.  DIR must be either `project-root' or one of
   (cdr project))
 
 (defvar project-files-relative-names nil
-  "When non-nil, `project-files' is allowed to return relative names.
-The names will be relative to the project root.  And this can only
-happen when all returned files are in the same directory. Meaning, the
-DIRS argument has to be nil or have only one element.")
+  "If non-nil, `project-files' is allowed to return relative file names.
+The file names should be relative to the project root.  And this can
+only happen when all returned files are in the same directory.
+In other words, the DIRS argument of `project-files' has to be nil or a
+list of only one element.")
 
 (cl-defgeneric project-files (project &optional dirs)
   "Return a list of files in directories DIRS in PROJECT.