diff --git a/bin/mod-tidy b/bin/mod-tidy
index b3d0971..77c279c 100755
--- a/bin/mod-tidy
+++ b/bin/mod-tidy
@@ -1,6 +1,5 @@
-#!/usr/bin/env bash
-
-set -xeuo pipefail
+#!/bin/sh
+set -eu
 
 cd "$(git rev-parse --show-toplevel)/"
 bazel run @go_sdk//:bin/go -- mod tidy
diff --git a/ci/test b/ci/test
index d397735..dd96eac 100755
--- a/ci/test
+++ b/ci/test
@@ -1,2 +1,2 @@
-#!/usr/bin/env sh
+#!/bin/sh
 exec bazel test "$@" ...
diff --git a/test/c/test.sh b/test/c/test.sh
index 7cfac79..fccb1ce 100755
--- a/test/c/test.sh
+++ b/test/c/test.sh
@@ -1,6 +1,5 @@
-#!/usr/bin/env bash
-
-set -euo pipefail
+#!/bin/sh
+set -eu
 
 # shellcheck disable=SC2153
 want=$WANT
diff --git a/toolchain/defs.bzl b/toolchain/defs.bzl
index 41aafe9..f495a52 100644
--- a/toolchain/defs.bzl
+++ b/toolchain/defs.bzl
@@ -103,13 +103,13 @@ set ZIG_GLOBAL_CACHE_DIR=%ZIG_LOCAL_CACHE_DIR%
 "{zig}" "{zig_tool}" %*
 """
 
-_ZIG_TOOL_WRAPPER_CACHE_KNOWN = """#!/usr/bin/env sh
+_ZIG_TOOL_WRAPPER_CACHE_KNOWN = """#!/bin/sh
 export ZIG_LOCAL_CACHE_DIR="{cache_prefix}/bazel-zig-cc"
 export ZIG_GLOBAL_CACHE_DIR="{cache_prefix}/bazel-zig-cc"
 exec "{zig}" "{zig_tool}" "$@"
 """
 
-_ZIG_TOOL_WRAPPER_CACHE_GUESS = """#!/usr/bin/env sh
+_ZIG_TOOL_WRAPPER_CACHE_GUESS = """#!/bin/sh
 set -e
 if [ -n "$TMPDIR" ]; then
     _cache_prefix=$TMPDIR