diff --git a/src/collectors/contributors.test.ts b/src/collectors/contributors.test.ts
index 3969540..e854ffa 100644
--- a/src/collectors/contributors.test.ts
+++ b/src/collectors/contributors.test.ts
@@ -11,6 +11,7 @@ test('returns unique human committers, sorted, skipping bots', async () => {
     { author: { login: 'dependabot[bot]', type: 'Bot' }, commit: { author: { name: 'd', date: '' } } },
     { author: { login: 'renovate[bot]', type: 'User' }, commit: { author: { name: 'r', date: '' } } },
     { author: null, commit: { author: null } },
+    { author: { type: 'User' }, commit: { author: { name: 'e', date: '' } } },
   ]);
 
   const result = await listActiveCommitters(client, { owner: 'acme', name: 'widgets' }, '2026-01-01T00:00:00Z');
diff --git a/src/collectors/contributors.ts b/src/collectors/contributors.ts
index 1902b4e..eba867e 100644
--- a/src/collectors/contributors.ts
+++ b/src/collectors/contributors.ts
@@ -4,7 +4,7 @@ import type { GithubClient } from '../github/GithubClient.ts';
 import type { ContributorSlice, RepoRef } from '../types.ts';
 
 interface ListCommitsItem {
-  author: { login: string; type?: string } | null;
+  author: { login?: string; type?: string } | null;
   commit: { author: { name: string; date: string } | null };
 }
 
@@ -24,7 +24,7 @@ export function listActiveCommitters(
       const logins = new Set<string>();
       for (const c of commits) {
         const author = c.author;
-        if (!author) continue;
+        if (!author?.login) continue;
         if (author.type === 'Bot') continue;
         if (author.login.endsWith('[bot]')) continue;
         logins.add(author.login);