diff --git a/README.md b/README.md
index 47462f86..6980f67a 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,10 @@ and permissions on Google Cloud.
     configure a Google Cloud Workload Identity Provider. See [setup](#setup)
     for instructions.
 
+-   You must run the `actions/checkout@v2` step _before_ this action. Omitting
+    the checkout step or putting it after `auth` will cause future steps to be
+    unable to authenticate.
+
 
 ## Usage
 
diff --git a/dist/main/index.js b/dist/main/index.js
index 43927f69..2b7a1533 100644
--- a/dist/main/index.js
+++ b/dist/main/index.js
@@ -2198,6 +2198,22 @@ function run() {
                 if (!githubWorkspace) {
                     throw new Error('$GITHUB_WORKSPACE is not set');
                 }
+                // There have been a number of issues where users have not used the
+                // "actions/checkout" step before our action. Our action relies on the
+                // creation of that directory; worse, if a user puts "actions/checkout"
+                // after our action, it will delete the exported credential. This
+                // following code does a small check to see if there are any files in the
+                // directory. It emits a warning if there are no files, since there may be
+                // legitimate use cases for authenticating without checking out the
+                // repository.
+                const githubWorkspaceIsEmpty = yield (0, utils_1.isEmptyDir)(githubWorkspace);
+                if (githubWorkspaceIsEmpty) {
+                    (0, core_1.warning)(`The "create_credentials_file" option is true, but the current ` +
+                        `GitHub workspace is empty. Did you forget to use ` +
+                        `"actions/checkout" before this step? If you do not intend to ` +
+                        `share authentication with future steps in this job, set ` +
+                        `"create_credentials_file" to false.`);
+                }
                 // Create credentials file.
                 const credentialsPath = yield client.createCredentialsFile(githubWorkspace);
                 (0, core_1.info)(`Created credentials file at "${credentialsPath}"`);
@@ -2292,12 +2308,22 @@ run();
 /***/ }),
 
 /***/ 314:
-/***/ ((__unused_webpack_module, exports) => {
+/***/ (function(__unused_webpack_module, exports, __nccwpck_require__) {
 
 "use strict";
 
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
 Object.defineProperty(exports, "__esModule", ({ value: true }));
-exports.buildDomainWideDelegationJWT = void 0;
+exports.isEmptyDir = exports.buildDomainWideDelegationJWT = void 0;
+const fs_1 = __nccwpck_require__(147);
 /**
  * buildDomainWideDelegationJWT constructs an _unsigned_ JWT to be used for a
  * DWD exchange. The JWT must be signed and then exchanged with the OAuth
@@ -2327,6 +2353,26 @@ function buildDomainWideDelegationJWT(serviceAccount, subject, scopes, lifetime)
     return JSON.stringify(body);
 }
 exports.buildDomainWideDelegationJWT = buildDomainWideDelegationJWT;
+/**
+ * isEmptyDir returns true if the given directory does not exist, or exists but
+ * contains no files. It also returns true if the current user does not have
+ * permission to read the directory, since it is effectively empty from the
+ * viewpoint of the caller.
+ *
+ * @param dir Path to a directory.
+ */
+function isEmptyDir(dir) {
+    return __awaiter(this, void 0, void 0, function* () {
+        try {
+            const files = yield fs_1.promises.readdir(dir);
+            return files.length <= 0;
+        }
+        catch (e) {
+            return true;
+        }
+    });
+}
+exports.isEmptyDir = isEmptyDir;
 
 
 /***/ }),
diff --git a/src/main.ts b/src/main.ts
index cba2680e..37f1c9ad 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -25,7 +25,7 @@ import { WorkloadIdentityClient } from './client/workload_identity_client';
 import { CredentialsJSONClient } from './client/credentials_json_client';
 import { AuthClient } from './client/auth_client';
 import { BaseClient } from './base';
-import { buildDomainWideDelegationJWT } from './utils';
+import { buildDomainWideDelegationJWT, isEmptyDir } from './utils';
 
 const secretsWarning =
   `If you are specifying input values via GitHub secrets, ensure the secret ` +
@@ -132,6 +132,25 @@ async function run(): Promise<void> {
         throw new Error('$GITHUB_WORKSPACE is not set');
       }
 
+      // There have been a number of issues where users have not used the
+      // "actions/checkout" step before our action. Our action relies on the
+      // creation of that directory; worse, if a user puts "actions/checkout"
+      // after our action, it will delete the exported credential. This
+      // following code does a small check to see if there are any files in the
+      // directory. It emits a warning if there are no files, since there may be
+      // legitimate use cases for authenticating without checking out the
+      // repository.
+      const githubWorkspaceIsEmpty = await isEmptyDir(githubWorkspace);
+      if (githubWorkspaceIsEmpty) {
+        logWarning(
+          `The "create_credentials_file" option is true, but the current ` +
+            `GitHub workspace is empty. Did you forget to use ` +
+            `"actions/checkout" before this step? If you do not intend to ` +
+            `share authentication with future steps in this job, set ` +
+            `"create_credentials_file" to false.`,
+        );
+      }
+
       // Create credentials file.
       const credentialsPath = await client.createCredentialsFile(githubWorkspace);
       logInfo(`Created credentials file at "${credentialsPath}"`);
diff --git a/src/utils.ts b/src/utils.ts
index 49163c1c..1375a177 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,5 +1,7 @@
 'use strict';
 
+import { promises as fs } from 'fs';
+
 /**
  * buildDomainWideDelegationJWT constructs an _unsigned_ JWT to be used for a
  * DWD exchange. The JWT must be signed and then exchanged with the OAuth
@@ -35,3 +37,20 @@ export function buildDomainWideDelegationJWT(
 
   return JSON.stringify(body);
 }
+
+/**
+ * isEmptyDir returns true if the given directory does not exist, or exists but
+ * contains no files. It also returns true if the current user does not have
+ * permission to read the directory, since it is effectively empty from the
+ * viewpoint of the caller.
+ *
+ * @param dir Path to a directory.
+ */
+export async function isEmptyDir(dir: string): Promise<boolean> {
+  try {
+    const files = await fs.readdir(dir);
+    return files.length <= 0;
+  } catch (e) {
+    return true;
+  }
+}
diff --git a/tests/utils.test.ts b/tests/utils.test.ts
index fff25157..5ab32a53 100644
--- a/tests/utils.test.ts
+++ b/tests/utils.test.ts
@@ -3,7 +3,9 @@
 import 'mocha';
 import { expect } from 'chai';
 
-import { buildDomainWideDelegationJWT } from '../src/utils';
+import { tmpdir } from 'os';
+
+import { buildDomainWideDelegationJWT, isEmptyDir } from '../src/utils';
 
 describe('Utils', () => {
   describe('#buildDomainWideDelegationJWT', () => {
@@ -54,4 +56,26 @@ describe('Utils', () => {
       });
     });
   });
+
+  describe('#isEmptyDir', async () => {
+    const cases = [
+      {
+        name: 'non-existent dir',
+        dir: '/this/path/definitely/does/not/exist',
+        exp: true,
+      },
+      {
+        name: 'exists',
+        dir: tmpdir(),
+        exp: false,
+      },
+    ];
+
+    cases.forEach((tc) => {
+      it(tc.name, async () => {
+        const isEmpty = await isEmptyDir(tc.dir);
+        expect(isEmpty).to.eq(tc.exp);
+      });
+    });
+  });
 });