diff --git a/Makefile b/Makefile
index 91a43ba18..c151c884f 100644
--- a/Makefile
+++ b/Makefile
@@ -24,9 +24,11 @@ autogen_pages: indxal.htm
 # built manually in a survex build tree.
 indxal.htm: noinfo/CAVETAB2.CSV noinfo/all.pos noinfo/make-indxal4.pl noinfo/areapage_skeletons/*.html noinfo/lengths.dat
 	python noinfo/make-areaindices.py
-	python noinfo/create_dplong_table.py
 	cd noinfo; perl ./make-indxal4.pl -q CAVETAB2.CSV
 
+noinfo/lengths.dat:
+	python noinfo/create_dplong_table.py
+
 noinfo/all.pos: noinfo/all.3d
 	3dtopos noinfo/all.3d noinfo/all.pos