diff --git a/src/scriptfile.c b/src/scriptfile.c
index 3508139..56186ff 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -2156,7 +2156,7 @@
 
     if (p == NULL)
 	return NULL;
-    prefix = vim_strsave(p);
+    prefix = strlow_save(p);
     if (prefix == NULL)
 	return NULL;