diff --git a/msdos/sedlisp.inp b/msdos/sedlisp.inp
index e2d2b755613..f02c24a9928 100644
--- a/msdos/sedlisp.inp
+++ b/msdos/sedlisp.inp
@@ -17,6 +17,9 @@
 #
 # ----------------------------------------------------------------------
 
+/^SHELL *=/i\
+export FNCASE=y
+
 /^lisp=/s|@srcdir@|.|
 /^VPATH=/s|@srcdir@|.|
 /^srcdir=/s|@srcdir@|.|