diff --git a/Makefile b/Makefile
index cff640c1c72131e62f2d5b838970ec5e131c2a22..adb9269227038a94268903d6a8a49a94fdd9461f 100644
--- a/Makefile
+++ b/Makefile
@@ -22,7 +22,7 @@ Makefile.coq: _CoqProject Makefile awk.Makefile
 build-dep/opam: opam
 	# Create the build-dep package.
 	@mkdir -p build-dep
-	@sed <opam 's/^\(build\|install\|remove\):.*/\1: []/; s/^name: *"\(.*\)" */name: "\1-builddep"/' > build-dep/opam
+	@sed <opam -E 's/^(build|install|remove):.*/\1: []/; s/^name: *"(.*)" */name: "\1-builddep"/' >build-dep/opam
 	@fgrep builddep build-dep/opam >/dev/null || (echo "sed failed to fix the package name" && exit 1) # sanity check
 
 build-dep: build-dep/opam phony