--- a/src/smtpd/smtpd_check.c
+++ b/src/smtpd/smtpd_check.c
@@ -5325,7 +5325,7 @@ char   *smtpd_check_queue(SMTPD_STATE *state)
      */
 #define BLOCKS(x)	((x) / fsbuf.block_size)
 
-    fsspace(".", &fsbuf);
+    fsspace("/overlay", &fsbuf);
     if (msg_verbose)
 	msg_info("%s: blocks %lu avail %lu min_free %lu msg_size_limit %lu",
 		 myname,
