diff --git a/programs/other/calcplus/Tupfile.lua b/programs/other/calcplus/Tupfile.lua
index 63ee1d4c1..6e5ed9a6c 100644
--- a/programs/other/calcplus/Tupfile.lua
+++ b/programs/other/calcplus/Tupfile.lua
@@ -1,2 +1,5 @@
 if tup.getconfig("NO_FASM") ~= "" then return end
-tup.rule("calcplus.asm", "fasm %f %o -dlang=" .. tup.getconfig("LANG") .. " %f %o" .. tup.getconfig("KPACK_CMD"), "%B")
+HELPERDIR = (tup.getconfig("HELPERDIR") == "") and "../.." or tup.getconfig("HELPERDIR")
+tup.include(HELPERDIR .. "/use_fasm.lua")
+tup.rule("calcplus.asm", FASM .. " -dlang=" .. tup.getconfig("LANG") .. " %f %o" .. tup.getconfig("KPACK_CMD"), "%B")
+