diff --git a/Makefile b/Makefile
index 8bc20f2b3..6a40189ae 100644
--- a/Makefile
+++ b/Makefile
@@ -34,9 +34,9 @@ $(UFODIR)/%.designspace: $(UFODIR)/%.glyphs $(UFODIR)/features | venv
 
 # UFOs from designspace
 $(UFODIR)/Inter-%Italic.ufo: $(UFODIR)/Inter-Italic.designspace | venv
-	. $(VENV) ; ./misc/tools/gen-instance-ufo.sh $< $@
+	. $(VENV) ; bash misc/tools/gen-instance-ufo.sh $< $@
 $(UFODIR)/Inter-%.ufo: $(UFODIR)/Inter-Roman.designspace | venv
-	. $(VENV) ; ./misc/tools/gen-instance-ufo.sh $< $@
+	. $(VENV) ; bash misc/tools/gen-instance-ufo.sh $< $@
 
 # make sure intermediate files are not rm'd by make
 .PRECIOUS: \
diff --git a/misc/tools/gen-instance-ufo.sh b/misc/tools/gen-instance-ufo.sh
index b8deb0632..61a1a1b4d 100755
--- a/misc/tools/gen-instance-ufo.sh
+++ b/misc/tools/gen-instance-ufo.sh
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 set -e
 PROG=${0##*/}
 DESIGNSPACE=$1