diff --git a/hledger/test/csvtest.sh b/hledger/test/csvtest.sh
index 061aad78d..0ba015117 100755
--- a/hledger/test/csvtest.sh
+++ b/hledger/test/csvtest.sh
@@ -1,4 +1,7 @@
-#!/bin/bash
+#!/usr/bin/env bash
+# POSIX sh would be better for folks on BSD, but unfortunately it has
+# a hard time doing the stderr filtering below.
+#
 #
 # This scripts expects stdin formatted like this:
 # <multi-line csv file>