diff --git a/dist/index.js b/dist/index.js
index a190e25..2015cc7 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -17512,39 +17512,72 @@ async function fetch_reviewers() {
   return [ ...reviewers ];
 }
 
-async function assign_reviewers(reviewers) {
+async function filter_only_collaborators(reviewers) {
   const context = get_context();
   const octokit = get_octokit();
 
   const [ teams_with_prefix, individuals ] = partition(reviewers, (reviewer) => reviewer.startsWith('team:'));
   const teams = teams_with_prefix.map((team_with_prefix) => team_with_prefix.replace('team:', ''));
 
-  const request_review_responses = [];
-
-  // Github's requestReviewers API will fail to add all reviewers if any of the aliases are not collaborators.
-  // Github also does not support a batch call to determine which aliases in the list are not collaborators.
-
-  // We therefore make each call individually so that we add all reviewers that are collaborators,
-  // and log failure for aliases that no longer have access.
+  // Create a list of requests for all available aliases and teams to see if they have permission
+  // to the PR associated with this action
+  const collaborator_responses = [];
   teams.forEach((team) => {
-    request_review_responses.push(octokit.pulls.requestReviewers({
+    collaborator_responses.push(octokit.teams.checkPermissionsForRepoInOrg({
+      org: context.repo.owner,
+      team_slug: team,
       owner: context.repo.owner,
       repo: context.repo.repo,
-      pull_number: context.payload.pull_request.number,
-      team_reviewers: [ team ],
+    }).then((response) => {
+      // https://docs.github.com/en/rest/teams/teams?apiVersion=2022-11-28#check-team-permissions-for-a-repository
+      // Its expected that a team with permission will return 204
+      core.info(`Received successful status code ${response?.status ?? 'Unknown'} for team: ${team}`);
+      return 'team:'.concat(team);
     }).catch((error) => core.error(`Team: ${team} failed to be added with error: ${error}`)));
   });
-
-  individuals.forEach((login) => {
-    request_review_responses.push(octokit.pulls.requestReviewers({
+  individuals.forEach((alias) => {
+    collaborator_responses.push(octokit.repos.checkCollaborator({
       owner: context.repo.owner,
       repo: context.repo.repo,
-      pull_number: context.payload.pull_request.number,
-      reviewers: [ login ],
-    }).catch((error) => core.error(`Individual: ${login} failed to be added with error: ${error}`)));
+      username: alias,
+    }).then((response) => {
+      // https://docs.github.com/en/rest/collaborators/collaborators?apiVersion=2022-11-28#check-if-a-user-is-a-repository-collaborator
+      // Its expected that a collaborator with permission will return 204
+      core.info(`Received successful status code ${response?.status ?? 'Unknown'} for alias: ${alias}`);
+      return alias;
+    }).catch((error) => core.error(`Individual: ${alias} failed to be added with error: ${error}`)));
   });
 
-  return Promise.allSettled(request_review_responses);
+  // Store the aliases and teams of all successful responses
+  const collaborators = [];
+  await Promise.allSettled(collaborator_responses).then((results) => {
+    results.forEach((result) => {
+      if (result?.value) {
+        collaborators.push(result?.value);
+      }
+    });
+  });
+
+  // Only include aliases and teams that exist as collaborators
+  const filtered_reviewers = reviewers.filter((reviewer) => collaborators.includes(reviewer));
+  core.info(`Filtered list of only collaborators ${filtered_reviewers.join(', ')}`);
+  return filtered_reviewers;
+}
+
+async function assign_reviewers(reviewers) {
+  const context = get_context();
+  const octokit = get_octokit();
+
+  const [ teams_with_prefix, individuals ] = partition(reviewers, (reviewer) => reviewer.startsWith('team:'));
+  const teams = teams_with_prefix.map((team_with_prefix) => team_with_prefix.replace('team:', ''));
+
+  return octokit.pulls.requestReviewers({
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    pull_number: context.payload.pull_request.number,
+    reviewers: individuals,
+    team_reviewers: teams,
+  });
 }
 
 /* Private */
@@ -17595,6 +17628,7 @@ module.exports = {
   fetch_config,
   fetch_changed_files,
   fetch_reviewers,
+  filter_only_collaborators,
   assign_reviewers,
   clear_cache,
 };
@@ -17683,6 +17717,9 @@ async function run() {
   core.info(`Possible Reviewers ${reviewers.join(', ')}, prepare filtering out already requested reviewers or approved reviewers`);
   reviewers = reviewers.filter((reviewer) => !requested_approved_reviewers.includes(reviewer));
 
+  core.info(`Possible New Reviewers ${reviewers.join(', ')}, prepare to filter to only collaborators`);
+  reviewers = await github.filter_only_collaborators(reviewers);
+
   core.info('Randomly picking reviewers if the number of reviewers is set');
   reviewers = randomly_pick_reviewers({ reviewers, config });
 
diff --git a/src/github.js b/src/github.js
index 3f2b051..6d31037 100644
--- a/src/github.js
+++ b/src/github.js
@@ -163,39 +163,72 @@ async function fetch_reviewers() {
   return [ ...reviewers ];
 }
 
-async function assign_reviewers(reviewers) {
+async function filter_only_collaborators(reviewers) {
   const context = get_context();
   const octokit = get_octokit();
 
   const [ teams_with_prefix, individuals ] = partition(reviewers, (reviewer) => reviewer.startsWith('team:'));
   const teams = teams_with_prefix.map((team_with_prefix) => team_with_prefix.replace('team:', ''));
 
-  const request_review_responses = [];
-
-  // Github's requestReviewers API will fail to add all reviewers if any of the aliases are not collaborators.
-  // Github also does not support a batch call to determine which aliases in the list are not collaborators.
-
-  // We therefore make each call individually so that we add all reviewers that are collaborators,
-  // and log failure for aliases that no longer have access.
+  // Create a list of requests for all available aliases and teams to see if they have permission
+  // to the PR associated with this action
+  const collaborator_responses = [];
   teams.forEach((team) => {
-    request_review_responses.push(octokit.pulls.requestReviewers({
+    collaborator_responses.push(octokit.teams.checkPermissionsForRepoInOrg({
+      org: context.repo.owner,
+      team_slug: team,
       owner: context.repo.owner,
       repo: context.repo.repo,
-      pull_number: context.payload.pull_request.number,
-      team_reviewers: [ team ],
+    }).then((response) => {
+      // https://docs.github.com/en/rest/teams/teams?apiVersion=2022-11-28#check-team-permissions-for-a-repository
+      // Its expected that a team with permission will return 204
+      core.info(`Received successful status code ${response?.status ?? 'Unknown'} for team: ${team}`);
+      return 'team:'.concat(team);
     }).catch((error) => core.error(`Team: ${team} failed to be added with error: ${error}`)));
   });
-
-  individuals.forEach((login) => {
-    request_review_responses.push(octokit.pulls.requestReviewers({
+  individuals.forEach((alias) => {
+    collaborator_responses.push(octokit.repos.checkCollaborator({
       owner: context.repo.owner,
       repo: context.repo.repo,
-      pull_number: context.payload.pull_request.number,
-      reviewers: [ login ],
-    }).catch((error) => core.error(`Individual: ${login} failed to be added with error: ${error}`)));
+      username: alias,
+    }).then((response) => {
+      // https://docs.github.com/en/rest/collaborators/collaborators?apiVersion=2022-11-28#check-if-a-user-is-a-repository-collaborator
+      // Its expected that a collaborator with permission will return 204
+      core.info(`Received successful status code ${response?.status ?? 'Unknown'} for alias: ${alias}`);
+      return alias;
+    }).catch((error) => core.error(`Individual: ${alias} failed to be added with error: ${error}`)));
+  });
+
+  // Store the aliases and teams of all successful responses
+  const collaborators = [];
+  await Promise.allSettled(collaborator_responses).then((results) => {
+    results.forEach((result) => {
+      if (result?.value) {
+        collaborators.push(result?.value);
+      }
+    });
   });
 
-  return Promise.allSettled(request_review_responses);
+  // Only include aliases and teams that exist as collaborators
+  const filtered_reviewers = reviewers.filter((reviewer) => collaborators.includes(reviewer));
+  core.info(`Filtered list of only collaborators ${filtered_reviewers.join(', ')}`);
+  return filtered_reviewers;
+}
+
+async function assign_reviewers(reviewers) {
+  const context = get_context();
+  const octokit = get_octokit();
+
+  const [ teams_with_prefix, individuals ] = partition(reviewers, (reviewer) => reviewer.startsWith('team:'));
+  const teams = teams_with_prefix.map((team_with_prefix) => team_with_prefix.replace('team:', ''));
+
+  return octokit.pulls.requestReviewers({
+    owner: context.repo.owner,
+    repo: context.repo.repo,
+    pull_number: context.payload.pull_request.number,
+    reviewers: individuals,
+    team_reviewers: teams,
+  });
 }
 
 /* Private */
@@ -246,6 +279,7 @@ module.exports = {
   fetch_config,
   fetch_changed_files,
   fetch_reviewers,
+  filter_only_collaborators,
   assign_reviewers,
   clear_cache,
 };
diff --git a/src/index.js b/src/index.js
index ece7a0e..2e3c35d 100644
--- a/src/index.js
+++ b/src/index.js
@@ -75,6 +75,9 @@ async function run() {
   core.info(`Possible Reviewers ${reviewers.join(', ')}, prepare filtering out already requested reviewers or approved reviewers`);
   reviewers = reviewers.filter((reviewer) => !requested_approved_reviewers.includes(reviewer));
 
+  core.info(`Possible New Reviewers ${reviewers.join(', ')}, prepare to filter to only collaborators`);
+  reviewers = await github.filter_only_collaborators(reviewers);
+
   core.info('Randomly picking reviewers if the number of reviewers is set');
   reviewers = randomly_pick_reviewers({ reviewers, config });
 
diff --git a/test/github.test.js b/test/github.test.js
index 85a3a73..223bfca 100644
--- a/test/github.test.js
+++ b/test/github.test.js
@@ -278,11 +278,15 @@ describe('github', function() {
     });
   });
 
-  describe('assign_reviewers()', function() {
-    const stub = sinon.stub();
+  describe('filter_only_collaborators()', function() {
+    const teamStub = sinon.stub();
+    const aliasStub = sinon.stub();
     const octokit = {
-      pulls: {
-        requestReviewers: stub,
+      repos: {
+        checkCollaborator: aliasStub,
+      },
+      teams: {
+        checkPermissionsForRepoInOrg: teamStub,
       },
     };
 
@@ -291,144 +295,145 @@ describe('github', function() {
       restoreModule = rewired_github.__set__('octokit_cache', octokit);
     });
     afterEach(function() {
-      stub.reset();
+      teamStub.reset();
+      aliasStub.reset();
       restoreModule();
     });
 
-    it('assigns reviewers - mixed success', async function() {
-      stub.onFirstCall().resolves({});
-      stub.onSecondCall().resolves({});
-      stub.onThirdCall().resolves({});
-
-      const reviewers = [ 'mario', 'princess-peach', 'team:koopa-troop' ];
-      await rewired_github.assign_reviewers(reviewers);
+    it('remove non collaborators - individual', async function() {
+      const allCandidates = [ 'bowser', 'peach', 'luigi', 'mario' ];
 
-      expect(stub.calledThrice).to.be.true;
-      expect(stub.firstCall.args[0]).to.deep.equal({
+      aliasStub.withArgs({
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        team_reviewers: [
-          'koopa-troop',
-        ],
-      });
-
-      expect(stub.secondCall.args[0]).to.deep.equal({
+        username: 'bowser',
+      }).rejects();
+      aliasStub.withArgs({
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        reviewers: [
-          'mario',
-        ],
-      });
-
-      expect(stub.thirdCall.args[0]).to.deep.equal({
+        username: 'peach',
+      }).resolves({ status: '204' });
+      aliasStub.withArgs({
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        reviewers: [
-          'princess-peach',
-        ],
-      });
+        username: 'luigi',
+      }).rejects();
+      aliasStub.withArgs({
+        owner: 'necojackarc',
+        repo: 'auto-request-review',
+        username: 'mario',
+      }).resolves({ status: '204' });
+
+      const actual = await rewired_github.filter_only_collaborators(allCandidates);
+      expect(actual).to.deep.equal([ 'peach', 'mario' ]);
+      expect(teamStub.called).to.be.false;
+      expect(aliasStub.callCount).to.be.equal(4);
     });
 
-    it('assigns reviewers - continues after failure individual', async function() {
-      stub.onFirstCall().resolves({});
-      let isResolved = false;
-      let isRejected = false;
-      const error = new Error('Alias is not a collaborator');
-      const failedNetworkCall = Promise.reject(error).then(
-        function(value) {
-          isResolved = true; return value;
-        },
-        function(error) {
-          isRejected = true; throw error;
-        }
-      );
-      stub.onSecondCall().returns(failedNetworkCall);
-      stub.onThirdCall().resolves({});
-
-      const reviewers = [ 'team:super_marios', 'princess-peach', 'luigi' ];
-      await rewired_github.assign_reviewers(reviewers);
+    it('remove non collaborators - teams', async function() {
+      const allCandidates = [ 'team:koopa-troop', 'team:toads', 'team:peach-alliance', 'team:bowser-and-co' ];
 
-      expect(stub.calledThrice).to.be.true;
-      expect(stub.firstCall.args[0]).to.deep.equal({
+      teamStub.withArgs({
+        org: 'necojackarc',
+        team_slug: 'koopa-troop',
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        team_reviewers: [
-          'super_marios',
-        ],
-      });
-
-      expect(stub.secondCall.args[0]).to.deep.equal({
+      }).resolves({ status: '204' });
+      teamStub.withArgs({
+        org: 'necojackarc',
+        team_slug: 'toads',
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        reviewers: [
-          'princess-peach',
-        ],
-      });
-      expect(isRejected).to.be.true;
-      expect(isResolved).to.be.false;
-
-      expect(stub.thirdCall.args[0]).to.deep.equal({
+      }).rejects();
+      teamStub.withArgs({
+        org: 'necojackarc',
+        team_slug: 'peach-alliance',
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        reviewers: [
-          'luigi',
-        ],
-      });
-    });
+      }).rejects();
+      teamStub.withArgs({
+        org: 'necojackarc',
+        team_slug: 'bowser-and-co',
+        owner: 'necojackarc',
+        repo: 'auto-request-review',
+      }).resolves({ status: '204' });
 
-    it('assigns reviewers - continues after failure team', async function() {
-      let isResolved = false;
-      let isRejected = false;
-      const error = new Error('Alias is not a collaborator');
-      const failedNetworkCall = Promise.reject(error).then(
-        function(value) {
-          isResolved = true; return value;
-        },
-        function(error) {
-          isRejected = true; throw error;
-        }
-      );
-      stub.onFirstCall().returns(failedNetworkCall);
-      stub.onSecondCall().resolves({});
-      stub.onThirdCall().resolves({});
-
-      const reviewers = [ 'team:toads', 'team:koopa-troop', 'mario' ];
-      await rewired_github.assign_reviewers(reviewers);
+      const actual = await rewired_github.filter_only_collaborators(allCandidates);
+      expect(actual).to.deep.equal([ 'team:koopa-troop', 'team:bowser-and-co' ]);
+      expect(teamStub.callCount).to.be.equal(4);
+      expect(aliasStub.called).to.be.false;
+    });
 
-      expect(stub.calledThrice).to.be.true;
+    it('remove non collaborators - mixed', async function() {
+      const allCandidates = [ 'peach', 'team:peach-alliance', 'luigi', 'mario', 'team:bowser-and-co' ];
 
-      expect(stub.firstCall.args[0]).to.deep.equal({
+      aliasStub.withArgs({
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        team_reviewers: [
-          'toads',
-        ],
-      });
-      expect(isRejected).to.be.true;
-      expect(isResolved).to.be.false;
+        username: 'peach',
+      }).resolves({ status: '204' });
+      aliasStub.withArgs({
+        owner: 'necojackarc',
+        repo: 'auto-request-review',
+        username: 'luigi',
+      }).rejects();
+      aliasStub.withArgs({
+        owner: 'necojackarc',
+        repo: 'auto-request-review',
+        username: 'mario',
+      }).rejects();
 
-      expect(stub.secondCall.args[0]).to.deep.equal({
+      teamStub.withArgs({
+        org: 'necojackarc',
+        team_slug: 'peach-alliance',
         owner: 'necojackarc',
-        pull_number: 18,
         repo: 'auto-request-review',
-        team_reviewers: [
-          'koopa-troop',
-        ],
-      });
+      }).resolves({ status: '204' });
+      teamStub.withArgs({
+        org: 'necojackarc',
+        team_slug: 'bowser-and-co',
+        owner: 'necojackarc',
+        repo: 'auto-request-review',
+      }).rejects();
 
-      expect(stub.thirdCall.args[0]).to.deep.equal({
+      const actual = await rewired_github.filter_only_collaborators(allCandidates);
+      expect(actual).to.deep.equal([ 'peach', 'team:peach-alliance' ]);
+      expect(teamStub.callCount).to.be.equal(2);
+      expect(aliasStub.callCount).to.be.equal(3);
+    });
+  });
+
+  describe('assign_reviewers()', function() {
+    const spy = sinon.spy();
+    const octokit = {
+      pulls: {
+        requestReviewers: spy,
+      },
+    };
+
+    let restoreModule;
+    beforeEach(function() {
+      restoreModule = rewired_github.__set__('octokit_cache', octokit);
+    });
+    afterEach(function() {
+      restoreModule();
+    });
+
+    it('assigns reviewers', async function() {
+      const reviewers = [ 'mario', 'princess-peach', 'team:koopa-troop' ];
+      await rewired_github.assign_reviewers(reviewers);
+
+      expect(spy.calledOnce).to.be.true;
+      expect(spy.lastCall.args[0]).to.deep.equal({
         owner: 'necojackarc',
         pull_number: 18,
         repo: 'auto-request-review',
         reviewers: [
           'mario',
+          'princess-peach',
+        ],
+        team_reviewers: [
+          'koopa-troop',
         ],
       });
     });
diff --git a/test/index.test.js b/test/index.test.js
index 7d1c377..6ad387c 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -15,6 +15,7 @@ describe('index', function() {
       sinon.stub(github, 'fetch_config');
       sinon.stub(github, 'fetch_changed_files');
       sinon.stub(github, 'fetch_reviewers');
+      sinon.stub(github, 'filter_only_collaborators');
       sinon.stub(github, 'assign_reviewers');
     });
 
@@ -23,6 +24,7 @@ describe('index', function() {
       github.fetch_config.restore();
       github.fetch_changed_files.restore();
       github.fetch_reviewers.restore();
+      github.filter_only_collaborators.restore();
       github.assign_reviewers.restore();
     });
 
@@ -54,6 +56,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -88,6 +92,8 @@ describe('index', function() {
       const current_reviewers = [ 'princess-peach' ];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -122,13 +128,15 @@ describe('index', function() {
       const current_reviewers = [ 'team:bowser-and-co' ];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
       expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'mario', 'team:peach-alliance', 'wario', 'waluigi' ]);
     });
 
-    it('skips caling assign if no reviewers', async function() {
+    it('skips calling assign if no reviewers', async function() {
       const config = {
         reviewers: {
           defaults: [ 'dr-mario' ],
@@ -156,11 +164,133 @@ describe('index', function() {
       const current_reviewers = [ 'princess-peach', 'mario' ];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.false;
     });
 
+    it('removes non collaborators - individual', async function() {
+      const config = {
+        reviewers: {
+          defaults: [ 'dr-mario' ],
+          groups: {
+            'mario-brothers': [ 'mario', 'luigi' ],
+          },
+        },
+        files: {
+          '**/*.js': [ 'mario-brothers', 'princess-peach' ],
+          '**/*.rb': [ 'wario', 'waluigi' ],
+        },
+      };
+      github.fetch_config.returns(config);
+
+      const pull_request = {
+        title: 'Nice Pull Request',
+        is_draft: false,
+        author: 'luigi',
+      };
+      github.get_pull_request.returns(pull_request);
+
+      const changed_files = [ 'path/to/file.js' ];
+      github.fetch_changed_files.returns(changed_files);
+
+      const current_reviewers = [ ];
+      github.fetch_reviewers.returns(current_reviewers);
+
+      const collaborators = [ 'mario' ];
+      github.filter_only_collaborators.returns(collaborators);
+
+      await run();
+
+      expect(github.filter_only_collaborators.calledOnce).to.be.true;
+      expect(github.filter_only_collaborators.lastCall.args[0]).to.have.members([ 'mario', 'princess-peach' ]);
+
+      expect(github.assign_reviewers.calledOnce).to.be.true;
+      expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'mario' ]);
+    });
+
+    it('removes non collaborators - team', async function() {
+      const config = {
+        reviewers: {
+          defaults: [ 'dr-mario' ],
+          groups: {
+            'mario-brothers': [ 'mario', 'luigi' ],
+          },
+        },
+        files: {
+          '**/*.js': [ 'mario-brothers', 'team:peach-alliance' ],
+          '**/*.rb': [ 'wario', 'waluigi', 'team:bowser-and-co' ],
+        },
+      };
+      github.fetch_config.returns(config);
+
+      const pull_request = {
+        title: 'Nice Pull Request',
+        is_draft: false,
+        author: 'luigi',
+      };
+      github.get_pull_request.returns(pull_request);
+
+      const changed_files = [ 'path/to/file.js', 'path/to/file.rb' ];
+      github.fetch_changed_files.returns(changed_files);
+
+      const current_reviewers = [ ];
+      github.fetch_reviewers.returns(current_reviewers);
+
+      const collaborators = [ 'team:peach-alliance' ];
+      github.filter_only_collaborators.returns(collaborators);
+
+      await run();
+
+      expect(github.filter_only_collaborators.calledOnce).to.be.true;
+      expect(github.filter_only_collaborators.lastCall.args[0]).to.have.members([ 'mario', 'team:peach-alliance', 'wario', 'waluigi', 'team:bowser-and-co' ]);
+
+      expect(github.assign_reviewers.calledOnce).to.be.true;
+      expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'team:peach-alliance' ]);
+    });
+
+    it('removes non collaborators + previous review mix', async function() {
+      const config = {
+        reviewers: {
+          defaults: [ 'dr-mario' ],
+          groups: {
+            'mario-brothers': [ 'mario', 'luigi' ],
+          },
+        },
+        files: {
+          '**/*.js': [ 'mario-brothers', 'team:peach-alliance' ],
+          '**/*.rb': [ 'wario', 'waluigi', 'team:bowser-and-co' ],
+        },
+      };
+      github.fetch_config.returns(config);
+
+      const pull_request = {
+        title: 'Nice Pull Request',
+        is_draft: false,
+        author: 'luigi',
+      };
+      github.get_pull_request.returns(pull_request);
+
+      const changed_files = [ 'path/to/file.js', 'path/to/file.rb' ];
+      github.fetch_changed_files.returns(changed_files);
+
+      const current_reviewers = [ 'waluigi', 'team:peach-alliance' ];
+      github.fetch_reviewers.returns(current_reviewers);
+
+      const collaborators = [ 'mario', 'team:bowser-and-co' ];
+      github.filter_only_collaborators.returns(collaborators);
+
+      await run();
+
+      expect(github.filter_only_collaborators.calledOnce).to.be.true;
+      expect(github.filter_only_collaborators.lastCall.args[0]).to.have.members([ 'mario', 'wario', 'team:bowser-and-co' ]);
+
+      expect(github.assign_reviewers.calledOnce).to.be.true;
+      expect(github.assign_reviewers.lastCall.args[0]).to.have.members([ 'mario', 'team:bowser-and-co' ]);
+    });
+
     it('requests review based on groups that author belongs to', async function() {
       const config = {
         reviewers: {
@@ -189,6 +319,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -248,6 +380,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.false;
@@ -280,6 +414,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.false;
@@ -313,6 +449,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -347,6 +485,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -381,6 +521,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;
@@ -413,6 +555,8 @@ describe('index', function() {
       const current_reviewers = [];
       github.fetch_reviewers.returns(current_reviewers);
 
+      github.filter_only_collaborators.returnsArg(0);
+
       await run();
 
       expect(github.assign_reviewers.calledOnce).to.be.true;