2 files changed, 4 insertions, 2 deletions

diff --git a/lisp/emulation/viper-ex.el b/lisp/emulation/viper-ex.el
index 783c01058e2..ecbcace2dd4 100644
--- a/lisp/emulation/viper-ex.el
+++ b/lisp/emulation/viper-ex.el
@@ -294,7 +294,8 @@
            "\\|"
            "bash$\\|bash.exe$"
            "\\)")
-          shell-file-name)))
+          shell-file-name)
+         t))
   "Is the user using a unix-type shell under a non-OS?"
   :type 'boolean)
 
diff --git a/lisp/emulation/viper-init.el b/lisp/emulation/viper-init.el
index 986d1fe6bc6..c39e3cf5142 100644
--- a/lisp/emulation/viper-init.el
+++ b/lisp/emulation/viper-init.el
@@ -47,7 +47,8 @@
 (defun viper-window-display-p ()
   (and window-system (not (memq window-system '(tty stream pc)))))
 
-(defcustom viper-ms-style-os-p (memq system-type '(ms-dos windows-nt))
+(defcustom viper-ms-style-os-p
+  (not (not (memq system-type '(ms-dos windows-nt))))
   "Non-nil if Emacs is running under an MS-style OS: MS-DOS, or MS-Windows."
   :type 'boolean
   :tag "Is it Microsoft-made OS?"