diff --git a/lib/external-queries.js b/lib/external-queries.js
index 253cf27622..90e0289383 100644
--- a/lib/external-queries.js
+++ b/lib/external-queries.js
@@ -11,8 +11,9 @@ const core = __importStar(require("@actions/core"));
 const exec = __importStar(require("@actions/exec"));
 const fs = __importStar(require("fs"));
 const path = __importStar(require("path"));
+const util = __importStar(require("./util"));
 async function checkoutExternalQueries(config) {
-    const folder = process.env['RUNNER_WORKSPACE'] || '/tmp/codeql-action';
+    const folder = util.getRequiredEnvParam('RUNNER_WORKSPACE');
     for (const externalQuery of config.externalQueries) {
         core.info('Checking out ' + externalQuery.repository);
         const checkoutLocation = path.join(folder, externalQuery.repository);
diff --git a/lib/util.js b/lib/util.js
index d12a91044f..a9d79bb416 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -15,6 +15,8 @@ const http = __importStar(require("@actions/http-client"));
 const auth = __importStar(require("@actions/http-client/auth"));
 const octokit = __importStar(require("@octokit/rest"));
 const console_log_level_1 = __importDefault(require("console-log-level"));
+const fs = __importStar(require("fs"));
+const os = __importStar(require("os"));
 const path = __importStar(require("path"));
 const sharedEnv = __importStar(require("./shared-environment"));
 /**
@@ -280,3 +282,11 @@ function getToolNames(sarifContents) {
     return Object.keys(toolNames);
 }
 exports.getToolNames = getToolNames;
+// Creates a random temporary directory, runs the given body, and then deletes the directory.
+// Mostly intended for use within tests.
+async function withTmpDir(body) {
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'codeql-action-'));
+    await body(tmpDir);
+    fs.rmdirSync(tmpDir, { recursive: true });
+}
+exports.withTmpDir = withTmpDir;
diff --git a/src/external-queries.test.ts b/src/external-queries.test.ts
index 088f3a3fef..a79f3f3e5c 100644
--- a/src/external-queries.test.ts
+++ b/src/external-queries.test.ts
@@ -3,15 +3,19 @@ import * as path from "path";
 
 import * as configUtils from "./config-utils";
 import * as externalQueries from "./external-queries";
+import * as util from "./util";
 
 test("checkoutExternalQueries", async () => {
     let config = new configUtils.Config();
     config.externalQueries = [
         new configUtils.ExternalQuery("github/codeql-go", "df4c6869212341b601005567381944ed90906b6b"),
     ];
-    await externalQueries.checkoutExternalQueries(config);
 
-    let destination = process.env["RUNNER_WORKSPACE"] || "/tmp/codeql-action/";
-    // COPYRIGHT file existed in df4c6869212341b601005567381944ed90906b6b but not in master
-    expect(fs.existsSync(path.join(destination, "github", "codeql-go", "COPYRIGHT"))).toBeTruthy();
+    await util.withTmpDir(async tmpDir => {
+        process.env["RUNNER_WORKSPACE"] = tmpDir;
+        await externalQueries.checkoutExternalQueries(config);
+
+        // COPYRIGHT file existed in df4c6869212341b601005567381944ed90906b6b but not in master
+        expect(fs.existsSync(path.join(tmpDir, "github", "codeql-go", "COPYRIGHT"))).toBeTruthy();
+    });
 });
diff --git a/src/external-queries.ts b/src/external-queries.ts
index c9724148d4..a478f538b0 100644
--- a/src/external-queries.ts
+++ b/src/external-queries.ts
@@ -4,9 +4,10 @@ import * as fs from 'fs';
 import * as path from 'path';
 
 import * as configUtils from './config-utils';
+import * as util from './util';
 
 export async function checkoutExternalQueries(config: configUtils.Config) {
-  const folder = process.env['RUNNER_WORKSPACE'] || '/tmp/codeql-action';
+  const folder = util.getRequiredEnvParam('RUNNER_WORKSPACE');
 
   for (const externalQuery of config.externalQueries) {
     core.info('Checking out ' + externalQuery.repository);
diff --git a/src/util.ts b/src/util.ts
index cfdd2419c1..d17571d5d5 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -3,6 +3,8 @@ import * as http from '@actions/http-client';
 import * as auth from '@actions/http-client/auth';
 import * as octokit from '@octokit/rest';
 import consoleLogLevel from 'console-log-level';
+import * as fs from "fs";
+import * as os from 'os';
 import * as path from 'path';
 
 import * as sharedEnv from './shared-environment';
@@ -313,3 +315,11 @@ export function getToolNames(sarifContents: string): string[] {
 
     return Object.keys(toolNames);
 }
+
+// Creates a random temporary directory, runs the given body, and then deletes the directory.
+// Mostly intended for use within tests.
+export async function withTmpDir(body: (tmpDir: string) => Promise<void>) {
+    const tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'codeql-action-'));
+    await body(tmpDir);
+    fs.rmdirSync(tmpDir, { recursive: true });
+}