diff --git a/src/apps/applets/tests/fixtures/applets.py b/src/apps/applets/tests/fixtures/applets.py
index 93cc6c15f64..1cffa66a509 100644
--- a/src/apps/applets/tests/fixtures/applets.py
+++ b/src/apps/applets/tests/fixtures/applets.py
@@ -364,6 +364,14 @@ async def applet_three(
         await teardown_applet(global_session, applet.id)
 
 
+@pytest.fixture
+async def lucy_applet_three_subject(session: AsyncSession, lucy: User, applet_three: AppletFull) -> SubjectSchema:
+    query = select(SubjectSchema).where(SubjectSchema.user_id == lucy.id, SubjectSchema.applet_id == applet_three.id)
+    res = await session.execute(query, execution_options={"synchronize_session": False})
+    model = res.scalars().one()
+    return model
+
+
 @pytest.fixture(autouse=True, scope="session")
 async def applet_four(
     global_session: AsyncSession,
diff --git a/src/apps/subjects/tests/tests.py b/src/apps/subjects/tests/tests.py
index cd3a5a719a5..68b82b39585 100644
--- a/src/apps/subjects/tests/tests.py
+++ b/src/apps/subjects/tests/tests.py
@@ -197,6 +197,40 @@ async def applet_one_lucy_reviewer_with_subject(
     return applet_one
 
 
+@pytest.fixture
+async def applet_three_lucy_owner(session: AsyncSession, applet_three: AppletFull, lucy) -> AppletFull:
+    await UserAppletAccessService(session, lucy.id, applet_three.id).add_role(lucy.id, Role.OWNER)
+    return applet_three
+
+
+@pytest.fixture
+async def applet_one_tom_owner(session: AsyncSession, applet_one: AppletFull, tom) -> AppletFull:
+    await UserAppletAccessService(session, tom.id, applet_one.id).add_role(tom.id, Role.OWNER)
+    return applet_one
+
+
+@pytest.fixture
+async def tom_invitation_payload(tom: User) -> dict:
+    return dict(
+        email=tom.email_encrypted,
+        first_name=tom.first_name,
+        last_name=tom.last_name,
+        language="en",
+        role=Role.MANAGER
+    )
+
+
+@pytest.fixture
+async def lucy_invitation_payload(lucy: User) -> dict:
+    return dict(
+        email=lucy.email_encrypted,
+        first_name=lucy.first_name,
+        last_name=lucy.last_name,
+        language="en",
+        role=Role.MANAGER
+    )
+
+
 class TestSubjects(BaseTest):
     fixtures = [
         "workspaces/fixtures/workspaces.json",
@@ -207,6 +241,10 @@ class TestSubjects(BaseTest):
     subject_detail_url = "/subjects/{subject_id}"
     subject_relation_url = "/subjects/{subject_id}/relations/{source_subject_id}"
     answer_url = "/answers"
+    invite_accept_url = "/invitations/{key}/accept"
+    invite_respondent_url = "/invitations/{applet_id}/respondent"
+    invite_manager_url = "/invitations/{applet_id}/managers"
+    workspace_respondents_url = "/workspaces/{owner_id}/respondents"
 
     async def test_create_subject(self, client, tom: User, applet_one: AppletFull, create_shell_body):
         creator_id = str(tom.id)
@@ -444,3 +482,66 @@ async def test_get_reviewer_subject(
         assert response.status_code == http.HTTPStatus.OK
         data = response.json()
         assert data
+
+    async def test_cross_invitation_must_have_no_duplicates(
+        self,
+        client,
+        session,
+        tom: User,
+        lucy: User,
+        applet_one_tom_owner: AppletFull,
+        applet_three_lucy_owner: AppletFull,
+        tom_applet_one_subject: Subject,
+        lucy_applet_three_subject: Subject,
+        lucy_invitation_payload,
+        tom_invitation_payload
+    ):
+        async def lucy_login():
+            await client.login(self.login_url, lucy.email_encrypted, "Test123")
+
+        async def tom_login():
+            await client.login(self.login_url, tom.email_encrypted, "Test1234!")
+
+        # Login as Tom and send invitation to Lucy
+        await tom_login()
+        res = await client.post(
+            self.invite_manager_url.format(applet_id=str(applet_one_tom_owner.id)),
+            lucy_invitation_payload
+        )
+        assert res.status_code == http.HTTPStatus.OK
+        lucy_invitation_key = res.json()["result"]["key"]
+
+        # Login as Lucy and send invitation to Tom
+        await lucy_login()
+        res = await client.post(
+            self.invite_manager_url.format(applet_id=str(applet_three_lucy_owner.id)),
+            tom_invitation_payload
+        )
+        assert res.status_code == http.HTTPStatus.OK
+        tom_invitation_key = res.json()["result"]["key"]
+
+        # Accept invitations
+        await tom_login()
+        tom_accept_url = self.invite_accept_url.format(key=tom_invitation_key)
+        res = await client.post(tom_accept_url)
+        assert res.status_code == http.HTTPStatus.OK
+
+        await lucy_login()
+        lucy_accept_url = self.invite_accept_url.format(key=lucy_invitation_key)
+        res = await client.post(lucy_accept_url)
+        assert res.status_code == http.HTTPStatus.OK
+
+        url_tom_respondents = self.workspace_respondents_url.format(owner_id=tom.id)
+        url_lucy_respondents = self.workspace_respondents_url.format(owner_id=lucy.id)
+
+        await tom_login()
+        res = await client.get(url_tom_respondents)
+        assert res.status_code == http.HTTPStatus.OK
+        tom_respondents_response = res.json()
+        assert tom_respondents_response["count"] == 2
+
+        await lucy_login()
+        res = await client.get(url_lucy_respondents)
+        assert res.status_code == http.HTTPStatus.OK
+        lucy_respondents_response = res.json()
+        assert lucy_respondents_response["count"] == 2
diff --git a/src/apps/workspaces/crud/user_applet_access.py b/src/apps/workspaces/crud/user_applet_access.py
index 247a355dad7..859082010e1 100644
--- a/src/apps/workspaces/crud/user_applet_access.py
+++ b/src/apps/workspaces/crud/user_applet_access.py
@@ -502,7 +502,9 @@ async def get_workspace_respondents(
             isouter=True,
         )
         query = query.where(
-            has_access, SubjectSchema.applet_id == applet_id if applet_id else True, SubjectSchema.soft_exists()
+            has_access,
+            UserAppletAccessSchema.owner_id == owner_id,
+            SubjectSchema.applet_id == applet_id if applet_id else True, SubjectSchema.soft_exists()
         )
 
         query = query.group_by(