diff --git a/test/beforeEach.js b/test/beforeEach.js
index 42830d44..34feda9f 100644
--- a/test/beforeEach.js
+++ b/test/beforeEach.js
@@ -1,13 +1,10 @@
 'use strict';
 
-const detectLibc = require('detect-libc');
 const sharp = require('../');
 
-const libcFamily = detectLibc.familySync();
-const usingCache = !(process.env.G_DEBUG || libcFamily === detectLibc.MUSL);
-const usingSimd = !(process.env.G_DEBUG || process.env.VIPS_NOVECTOR);
-const concurrency = process.env.VIPS_CONCURRENCY ||
-  (libcFamily === detectLibc.MUSL || process.arch === 'arm' ? 1 : undefined);
+const usingCache = !process.env.G_DEBUG;
+const usingSimd = !process.env.VIPS_NOVECTOR;
+const concurrency = Number(process.env.VIPS_CONCURRENCY) || 0;
 
 exports.mochaHooks = {
   beforeEach () {
diff --git a/test/leak/leak.sh b/test/leak/leak.sh
index f21609e5..d706d11a 100755
--- a/test/leak/leak.sh
+++ b/test/leak/leak.sh
@@ -8,7 +8,7 @@ fi
 curl -s -o ./test/leak/libvips.supp https://raw.githubusercontent.com/libvips/libvips/master/suppressions/valgrind.supp
 
 for test in ./test/unit/*.js; do
-  G_SLICE=always-malloc G_DEBUG=gc-friendly VIPS_LEAK=1 valgrind \
+  G_SLICE=always-malloc G_DEBUG=gc-friendly VIPS_LEAK=1 VIPS_NOVECTOR=1 valgrind \
     --suppressions=test/leak/libvips.supp \
     --suppressions=test/leak/sharp.supp \
     --gen-suppressions=yes \