diff --git a/lib/utils.js b/lib/utils.js
index bc955b8..23add21 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -20,7 +20,7 @@ var which = require("which");
  * @return {Promise}
  */
 function normalizeBinary (binaryPath, platform, arch) {
-  return new Promise(function(resolve, reject) {
+  return new Promise(function(resolve) {
     platform = platform || os.platform();
     arch = arch || os.arch();
     binaryPath = binaryPath || process.env.JPM_FIREFOX_BINARY || "firefox";
@@ -66,13 +66,7 @@ function normalizeBinary (binaryPath, platform, arch) {
     // On linux but no path yet, use which to try and find the binary
     else if (platform.indexOf("linux") !== -1) {
         binaryPath = normalizeBinary.appNames[binaryPath + " on linux"] || binaryPath;
-        which(binaryPath, function(err, resolvedPath) {
-          if (err) {
-            reject(err);
-          } else {
-            resolve(resolvedPath);
-          }
-        });
+        resolve(which(binaryPath));
         return;
     }
     // No action needed on windows if it's an executable already
diff --git a/package-lock.json b/package-lock.json
index f8b2546..b92f6de 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -376,14 +376,6 @@
       "integrity": "sha1-Yzwsg+PaQqUC9SRmAiSA9CCCYd4=",
       "dev": true
     },
-    "is-absolute": {
-      "version": "0.1.7",
-      "resolved": "https://registry.npmjs.org/is-absolute/-/is-absolute-0.1.7.tgz",
-      "integrity": "sha1-hHSREZ/MtftDYhfMc39/qtUPYD8=",
-      "requires": {
-        "is-relative": "^0.1.0"
-      }
-    },
     "is-binary-path": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/is-binary-path/-/is-binary-path-2.1.0.tgz",
@@ -426,11 +418,6 @@
       "integrity": "sha512-YWnfyRwxL/+SsrWYfOpUtz5b3YD+nyfkHvjbcanzk8zgyO4ASD67uVMRt8k5bM4lLMDnXfriRhOpemw+NfT1eA==",
       "dev": true
     },
-    "is-relative": {
-      "version": "0.1.3",
-      "resolved": "https://registry.npmjs.org/is-relative/-/is-relative-0.1.3.tgz",
-      "integrity": "sha1-kF/uiuhvRbPsYUvDwVyGnfCHboI="
-    },
     "is-unicode-supported": {
       "version": "0.1.0",
       "resolved": "https://registry.npmjs.org/is-unicode-supported/-/is-unicode-supported-0.1.0.tgz",
@@ -438,9 +425,9 @@
       "dev": true
     },
     "isexe": {
-      "version": "1.1.2",
-      "resolved": "https://registry.npmjs.org/isexe/-/isexe-1.1.2.tgz",
-      "integrity": "sha1-NvPiLmB1CSD15yQaR2qMakInWtA="
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/isexe/-/isexe-3.1.1.tgz",
+      "integrity": "sha512-LpB/54B+/2J5hqQ7imZHfdU31OlgQqx7ZicVlkm9kzg9/w8GKLEcFfJl/t7DCEDueOyBAD6zCCwTO6Fzs0NoEQ=="
     },
     "js-yaml": {
       "version": "4.1.0",
@@ -714,12 +701,11 @@
       "dev": true
     },
     "which": {
-      "version": "1.2.4",
-      "resolved": "https://registry.npmjs.org/which/-/which-1.2.4.tgz",
-      "integrity": "sha1-FVf5YIBgTlsRs1meufRbUKnv1yI=",
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/which/-/which-4.0.0.tgz",
+      "integrity": "sha512-GlaYyEb07DPxYCKhKzplCWBJtvxZcZMrL+4UkrTSJHHPyZU4mYYTv3qaOe77H7EODLSSopAUFAc6W8U4yqvscg==",
       "requires": {
-        "is-absolute": "^0.1.7",
-        "isexe": "^1.1.1"
+        "isexe": "^3.1.1"
       }
     },
     "winreg": {
diff --git a/package.json b/package.json
index 85cf252..448a20a 100644
--- a/package.json
+++ b/package.json
@@ -23,7 +23,7 @@
   "dependencies": {
     "commander": "2.9.0",
     "shell-quote": "1.8.1",
-    "which": "1.2.4",
+    "which": "^4.0.0",
     "winreg": "0.0.12"
   },
   "devDependencies": {
diff --git a/test/run/test.utils.js b/test/run/test.utils.js
index 0f335bc..b80124f 100644
--- a/test/run/test.utils.js
+++ b/test/run/test.utils.js
@@ -12,6 +12,10 @@ var sandbox = require('sandboxed-module');
 var binary = utils.normalizeBinary;
 
 sandbox.configure({
+  requires: {
+    // sandboxed-module is unable to find this module directly
+    "fs/promises": require("fs/promises"),
+  },
   globals: {
     // As of Node 12.x, the process global is no longer an enumerable property of the global.
     // https://github.com/nodejs/node/pull/26882
@@ -160,9 +164,7 @@ describe("lib/utils", function () {
 
     var binary = sandbox.require("../../lib/utils", {
       requires: {
-        which: function(bin, callback) {
-          callback(null, "/usr/bin/" + bin);
-        }
+        which: async (bin) => "/usr/bin/" + bin
       }
     }).normalizeBinary;
 
@@ -247,9 +249,7 @@ describe("lib/utils", function () {
 
     var binary = sandbox.require("../../lib/utils", {
       requires: {
-        which: function(bin, callback) {
-          callback(null, "/usr/bin/" + bin);
-        }
+        which: async (bin) => "/usr/bin/" + bin
       }
     }).normalizeBinary;