diff --git a/Makefile b/Makefile
index e0e5d21..1fc22ae 100644
--- a/Makefile
+++ b/Makefile
@@ -22,7 +22,7 @@ venv-test: venv-test/touchfile
 
 build.stamp: venv .init.stamp sources/config.yaml $(SOURCES)
 	rm -rf fonts
-	(for config in sources/config*.yaml; do . venv/bin/activate; gftools builder $$config; done) && touch build.stamp
+	(for config in sources/config*.yaml; do . venv/bin/activate; gftools builder $$config; done) && ./build_instances.sh && touch build.stamp
 
 .init.stamp: venv
 	. venv/bin/activate; python3 scripts/first-run.py
diff --git a/build_instances.sh b/build_instances.sh
index 0bf7f8e..f10da9f 100755
--- a/build_instances.sh
+++ b/build_instances.sh
@@ -1,2 +1,4 @@
+#!/bin/bash
+
 fonttools varLib.instancer fonts/variable/Urbanist\[ital,wght\].ttf ital=0 -o fonts/variable/Urbanist\[wght\].ttf --update-name-table
 fonttools varLib.instancer fonts/variable/Urbanist\[ital,wght\].ttf ital=1 -o fonts/variable/Urbanist-Italic\[wght\].ttf --update-name-table