diff --git a/src/eval.c b/src/eval.c
index 9091f79..55d61e7 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -26440,8 +26440,10 @@
     if (src[*usedlen] == ':' && src[*usedlen + 1] == 'S')
     {
 	/* vim_strsave_shellescape() needs a NUL terminated string. */
+	c = (*fnamep)[*fnamelen];
 	(*fnamep)[*fnamelen] = NUL;
 	p = vim_strsave_shellescape(*fnamep, FALSE, FALSE);
+	(*fnamep)[*fnamelen] = c;
 	if (p == NULL)
 	    return -1;
 	vim_free(*bufp);