diff --git a/Makefile_happysrcs b/Makefile_happysrcs
index f4041ee..2f464a1 100644
--- a/Makefile_happysrcs
+++ b/Makefile_happysrcs
@@ -1,10 +1,11 @@
+GHC_VERSION = $(shell ghc --numeric-version)
 HAPPY = happy
 HAPPY_OPTS = -a -g -c -i/tmp/t.info
 ALEX = alex
 ALEX_OPTS = -g
 
 SRC = src
-CABAL_BUILD = dist-newstyle/build/x86_64-osx/ghc-9.6.2/rlp-0.1.0.0/build
+CABAL_BUILD = $(shell clisp find-build.cl)
 
 all: parsers lexers
 
diff --git a/find-build.cl b/find-build.cl
new file mode 100755
index 0000000..f445199
--- /dev/null
+++ b/find-build.cl
@@ -0,0 +1,8 @@
+#!/usr/bin/env clisp
+
+(let* ((paths (directory "dist-newstyle/build/*/*/rlp-*/build/"))
+       (n (length paths)))
+  (cond ((< 1 n) (error ">1 build directories found. run `cabal clean`."))
+        ((< n 1) (error "no build directories found. this shouldn't happen lol"))
+        (t       (format t "~A" (car paths)))))
+