diff --git a/Makefile b/Makefile
index 4a1cefdbc..d235e6d71 100644
--- a/Makefile
+++ b/Makefile
@@ -94,7 +94,7 @@ noinfo/alltracks.3d: $(shell $(svxtrace_cmd) $(dataset_path)/fixedpts/gps/tracks
 
 #this requires ttf-freefont package to be installed
 #And dump3d from survex
-prospecting_guide: 3dfiles freefont dump3d
+prospecting_guide: 3dfiles freefont noinfo/lengths.dat
 	cd noinfo/prospecting_guide_scripts && python make-prospectingguide-new.py
 	cd noinfo/prospecting_guide_scripts && python make-prospectingguide-new.py --white