diff --git a/build/basics.tcl b/build/basics.tcl
index 276bcf26..3c0c6a1a 100644
--- a/build/basics.tcl
+++ b/build/basics.tcl
@@ -12,6 +12,9 @@ respond "*" ":rename .;@ nits, .;@ its\r"
 # Free up some disk space on the pack holding most source code.
 gfr_second
 
+# Gague free disk blocks.
+respond "*" ":listf sys\r"
+
 respond "*" ":print sys1;..new. (udir)\r"
 type ":vk\r"
 respond "*" ":print sys2;..new. (udir)\r"
diff --git a/build/mark.tcl b/build/mark.tcl
index 94cf8ac1..72420f7a 100644
--- a/build/mark.tcl
+++ b/build/mark.tcl
@@ -28,6 +28,9 @@ expect -timeout 3000 "E-O-T"
 respond "_" "quit\r"
 expect ":KILL"
 
+# Gague free disk blocks.
+respond "*" ":listf sys\r"
+
 respond "*" ":print sysbin;..new. (udir)\r"
 type ":vk\r"
 respond "*" ":midas sysbin;_midas;midas\r"