1 files changed, 3 insertions, 1 deletions

diff --git a/src/fileio.c b/src/fileio.c
index bbd1a4ef69c..0a52982291d 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -755,7 +755,9 @@ For technical reasons, this function can return correct but
 non-intuitive results for the root directory; for instance,
 \(expand-file-name ".." "/") returns "/..".  For this reason, use
 \(directory-file-name (file-name-directory dirname)) to traverse a
-filesystem tree, not (expand-file-name ".." dirname).  */)
+filesystem tree, not (expand-file-name ".." dirname).  Note: make
+sure DIRNAME in this example doesn't end in a slash, unless it's
+the root directory.  */)
   (Lisp_Object name, Lisp_Object default_directory)
 {
   /* These point to SDATA and need to be careful with string-relocation