diff --git a/pkgs/build-support/fetchhg/nix-prefetch-hg b/pkgs/build-support/fetchhg/nix-prefetch-hg
index a877b217125f..7143eecfe5c6 100755
--- a/pkgs/build-support/fetchhg/nix-prefetch-hg
+++ b/pkgs/build-support/fetchhg/nix-prefetch-hg
@@ -1,4 +1,5 @@
-#! /bin/sh -e
+#! /usr/bin/env bash
+set -e
 
 url=$1
 rev=$2