1 files changed, 3 insertions, 1 deletions

diff --git a/lisp/shell.el b/lisp/shell.el
index c5e5cbbee7e..ea7f0beebb0 100644
--- a/lisp/shell.el
+++ b/lisp/shell.el
@@ -264,7 +264,9 @@ see the function `dirtrack-mode'."
   :group 'shell-directories)
 
 (defcustom explicit-shell-file-name nil
-  "If non-nil, is file name to use for explicitly requested inferior shell."
+  "If non-nil, is file name to use for explicitly requested inferior shell.
+When nil, such interactive shell sessions fallback to using either
+the shell specified in $ESHELL or in `shell-file-name'."
   :type '(choice (const :tag "None" nil) file)
   :group 'shell)