diff --git a/build/rust-version b/build/rust-version
index 4f02b123..e500392d 100755
--- a/build/rust-version
+++ b/build/rust-version
@@ -1,7 +1,11 @@
-#!/bin/sh
+#! /usr/bin/env bash
+set -euo pipefail
 
-if ! version=$(grep -m 1 -oP "channel\s*=\s*\K(.*)" rust-toolchain.toml); then
-  echo "fatal: no rust version found via rust-toolchain.toml" >&2 ; exit 1
+if ! version=$(grep -m 1 -oP '^\s*channel\s*=\s*"?\K([\d\.]+)' rust-toolchain.toml)
+then
+  echo "fatal: no rust version found via rust-toolchain.toml" >&2
+  exit 1
+else
+  echo "$version"
 fi
 
-echo "$version"