diff --git a/src/autoupdater.ts b/src/autoupdater.ts
index 93875d47..f95d1032 100644
--- a/src/autoupdater.ts
+++ b/src/autoupdater.ts
@@ -246,18 +246,27 @@ export class AutoUpdater {
       return false;
     }
 
-    const { data: comparison } = await this.octokit.rest.repos.compareCommits({
-      owner: pull.head.repo.owner.login,
-      repo: pull.head.repo.name,
-      // This base->head, head->base logic is intentional, we want
-      // to see what would happen if we merged the base into head not
-      // vice-versa.
-      base: pull.head.label,
-      head: pull.base.label,
-    });
-
-    if (comparison.behind_by === 0) {
-      ghCore.info('Skipping pull request, up-to-date with base branch.');
+    try {
+      const { data: comparison } =
+        await this.octokit.rest.repos.compareCommitsWithBasehead({
+          owner: pull.head.repo.owner.login,
+          repo: pull.head.repo.name,
+          // This base->head, head->base logic is intentional, we want
+          // to see what would happen if we merged the base into head not
+          // vice-versa. This parameter expects the format {base}...{head}.
+          basehead: `${pull.head.label}...${pull.base.label}`,
+        });
+
+      if (comparison.behind_by === 0) {
+        ghCore.info('Skipping pull request, up-to-date with base branch.');
+        return false;
+      }
+    } catch (e: unknown) {
+      if (e instanceof Error) {
+        ghCore.error(
+          `Caught error trying to compare base with head: ${e.message}`,
+        );
+      }
       return false;
     }
 
diff --git a/test/autoupdate.test.ts b/test/autoupdate.test.ts
index f4e68f12..3af125bc 100644
--- a/test/autoupdate.test.ts
+++ b/test/autoupdate.test.ts
@@ -1099,6 +1099,21 @@ describe('test `merge`', () => {
     }
   });
 
+  test('handles errors from compareCommitsWithBasehead', async () => {
+    (config.retryCount as jest.Mock).mockReturnValue(0);
+    const updater = new AutoUpdater(config, emptyEvent);
+
+    const scope = nock('https://api.github.com:443')
+      .get(`/repos/${owner}/${repo}/compare/${head}...${base}`)
+      .reply(404, {
+        message: 'Not Found',
+      });
+
+    const needsUpdate = await updater.update(owner, <any>validPull);
+    expect(needsUpdate).toEqual(false);
+    expect(scope.isDone()).toEqual(true);
+  });
+
   test('handles fork authorisation errors', async () => {
     (config.retryCount as jest.Mock).mockReturnValue(0);
     const updater = new AutoUpdater(config, emptyEvent);