diff --git a/src/filepath.c b/src/filepath.c
index 89fafe3..347612a 100644
--- a/src/filepath.c
+++ b/src/filepath.c
@@ -876,7 +876,7 @@
 {
     char_u *p = NULL;
 
-    if (in_vim9script() && check_for_string(&argvars[0]) == FAIL)
+    if (in_vim9script() && check_for_nonempty_string(&argvars[0]) == FAIL)
 	return;
     (void)mch_can_exe(tv_get_string(&argvars[0]), &p, TRUE);
     rettv->v_type = VAR_STRING;
@@ -942,7 +942,7 @@
 
     rettv->vval.v_string = NULL;
     rettv->v_type = VAR_STRING;
-    if (in_vim9script() && check_for_string(&argvars[0]) == FAIL)
+    if (in_vim9script() && check_for_nonempty_string(&argvars[0]) == FAIL)
 	return;
 
 #ifdef FEAT_SEARCHPATH
@@ -1028,9 +1028,9 @@
 	return;
     fname = tv_get_string_chk(&argvars[0]);
     mods = tv_get_string_buf_chk(&argvars[1], buf);
-    if (fname == NULL || mods == NULL)
+    if (fname == NULL)
 	fname = NULL;
-    else
+    else if (mods != NULL && *mods != NUL)
     {
 	len = (int)STRLEN(fname);
 	(void)modify_fname(mods, FALSE, &usedlen, &fname, &fbuf, &len);