diff --git a/tools/refresh.conf b/tools/refresh.conf
index 98f709f..a653b03 100644
--- a/tools/refresh.conf
+++ b/tools/refresh.conf
@@ -3,10 +3,18 @@
 # BUILD_CMD runs from <repo>/<BUILD_DIR> with $PREFIX (the libmeos install prefix) and $CATALOG
 # exported; $SKIP_TESTS is set when --skip-tests is passed. tools/codegen.py reads the catalog
 # staged at CATALOG_DEST and regenerates the committed functions/ package.
+#
+# PKG_CONFIG_PATH names the prefix this run just built. functions/cgo.go says
+# `#cgo pkg-config: meos`, so cgo resolves whichever meos.pc the default search path answers
+# with -- an older install under /usr/local otherwise wins, and it publishes none of the
+# -D<FAMILY>=1 defines the fresh meos.pc carries. Each declaration then stays behind its
+# `#if` and the build fails naming a symbol the header does declare. The include path comes
+# from the same meos.pc, and the h3 one from cgo.go's own `#cgo linux CFLAGS`, so no
+# CGO_CFLAGS is needed here.
 ENGINE=go
 BUILD_DIR=.
 BUILD_LIBMEOS=true
 CATALOG_DEST=tools/meos-idl.json
 BUILD_CMD='python3 tools/codegen.py
-  CGO_CFLAGS="-I$PREFIX/include -I/usr/include/h3" CGO_LDFLAGS="-L$PREFIX/lib -lmeos" LD_LIBRARY_PATH="$PREFIX/lib" go build ./functions
+  PKG_CONFIG_PATH="$PREFIX/lib/pkgconfig" CGO_LDFLAGS="-L$PREFIX/lib -lmeos" LD_LIBRARY_PATH="$PREFIX/lib" go build ./functions
   [ -n "${SKIP_TESTS:-}" ] || CGO_ENABLED=0 go test ./tools/parity/'