diff --git a/packages/v1-ready/hubspot/api.js b/packages/v1-ready/hubspot/api.js
index d0c0eda..9276811 100644
--- a/packages/v1-ready/hubspot/api.js
+++ b/packages/v1-ready/hubspot/api.js
@@ -213,13 +213,19 @@ class Api extends OAuth2Requester {
             properties = await this._propertiesList('contact');
         }
 
+        const query = { limit, properties };
+        // HubSpot rejects `after=null`/`after=` with a 400, so only send the
+        // paging cursor once we actually have one (i.e. from the second page
+        // onward). Without this guard, paging past the first page is impossible
+        // and callers are forced onto the search endpoint, which is hard-capped
+        // at 10,000 results.
+        if (after !== null && after !== undefined && after !== '') {
+            query.after = after;
+        }
+
         const options = {
             url: this.baseUrl + this.URLs.contacts,
-            query: {
-                limit,
-                after,
-                properties,
-            }
+            query,
         };
 
         return this._get(options);
diff --git a/packages/v1-ready/hubspot/tests/listContacts.test.js b/packages/v1-ready/hubspot/tests/listContacts.test.js
new file mode 100644
index 0000000..9a2dd53
--- /dev/null
+++ b/packages/v1-ready/hubspot/tests/listContacts.test.js
@@ -0,0 +1,50 @@
+/**
+ * Unit tests for Api.listContacts pagination query-building.
+ *
+ * The module's other tests (api.test.js) are live-OAuth integration tests that
+ * require real HubSpot credentials. These are fast unit tests that stub the
+ * underlying `_get` so we can assert the request query without a network call.
+ */
+const { Api } = require('../api');
+
+describe('Api.listContacts pagination', () => {
+    function makeApi() {
+        const api = new Api({});
+        api._get = jest.fn().mockResolvedValue({ results: [], paging: {} });
+        return api;
+    }
+
+    it('omits `after` from the query on the first page (no cursor)', async () => {
+        const api = makeApi();
+        await api.listContacts({ limit: 100, properties: ['email'] });
+
+        expect(api._get).toHaveBeenCalledTimes(1);
+        const { query } = api._get.mock.calls[0][0];
+        // HubSpot 400s on `after=null`; the first page must not send it at all.
+        expect(query).not.toHaveProperty('after');
+        expect(query.limit).toBe(100);
+        expect(query.properties).toEqual(['email']);
+    });
+
+    it('sends `after` from the second page onward', async () => {
+        const api = makeApi();
+        await api.listContacts({
+            after: '12345',
+            limit: 100,
+            properties: ['email'],
+        });
+
+        expect(api._get.mock.calls[0][0].query.after).toBe('12345');
+    });
+
+    it('treats null `after` as "no cursor"', async () => {
+        const api = makeApi();
+        await api.listContacts({
+            after: null,
+            limit: 100,
+            properties: ['email'],
+        });
+
+        expect(api._get.mock.calls[0][0].query).not.toHaveProperty('after');
+    });
+});