diff --git a/lib/interfaces/common.js b/lib/interfaces/common.js
index 7997312786..3d31ab7eb2 100644
--- a/lib/interfaces/common.js
+++ b/lib/interfaces/common.js
@@ -108,6 +108,16 @@ module.exports = function(suites, context, mocha) {
         suite.file = opts.file;
         suites.unshift(suite);
         if (opts.isOnly) {
+          if (
+            mocha.options.forbidOnly &&
+            (!mocha.options.grep ||
+              (mocha.options.grep &&
+                mocha.options.grep.test(suite.fullTitle()) &&
+                !mocha.options.invert))
+          ) {
+            throw new Error('`.only` forbidden');
+          }
+
           suite.parent._onlySuites = suite.parent._onlySuites.concat(suite);
         }
         if (typeof opts.fn === 'function') {
diff --git a/test/integration/fixtures/options/forbid-only/only-empty-suite.js b/test/integration/fixtures/options/forbid-only/only-empty-suite.js
new file mode 100644
index 0000000000..d11a38fa55
--- /dev/null
+++ b/test/integration/fixtures/options/forbid-only/only-empty-suite.js
@@ -0,0 +1,3 @@
+'use strict';
+
+describe.only('forbid only - suite marked with only', function() {});
diff --git a/test/integration/helpers.js b/test/integration/helpers.js
index ea8182b235..0c55362046 100644
--- a/test/integration/helpers.js
+++ b/test/integration/helpers.js
@@ -64,7 +64,7 @@ module.exports = {
         var result = JSON.parse(res.output);
         result.code = res.code;
       } catch (err) {
-        return fn(err);
+        return fn(new Error('output is not valid JSON:\n\n' + res.output));
       }
 
       fn(null, result);
diff --git a/test/integration/options.spec.js b/test/integration/options.spec.js
index 14035e054b..1251333a45 100644
--- a/test/integration/options.spec.js
+++ b/test/integration/options.spec.js
@@ -2,7 +2,8 @@
 
 var path = require('path');
 var helpers = require('./helpers');
-var run = helpers.runMochaJSON;
+var runMochaJSON = helpers.runMochaJSON;
+var runMocha = helpers.runMocha;
 var runRaw = helpers.runMochaJSONRaw;
 var directInvoke = helpers.invokeMocha;
 var resolvePath = helpers.resolveFixturePath;
@@ -15,7 +16,10 @@ describe('options', function() {
     });
 
     it('should fail synchronous specs', function(done) {
-      run('options/async-only-sync.fixture.js', args, function(err, res) {
+      runMochaJSON('options/async-only-sync.fixture.js', args, function(
+        err,
+        res
+      ) {
         if (err) {
           done(err);
           return;
@@ -26,7 +30,10 @@ describe('options', function() {
     });
 
     it('should allow asynchronous specs', function(done) {
-      run('options/async-only-async.fixture.js', args, function(err, res) {
+      runMochaJSON('options/async-only-async.fixture.js', args, function(
+        err,
+        res
+      ) {
         if (err) {
           done(err);
           return;
@@ -43,7 +50,7 @@ describe('options', function() {
     });
 
     it('should stop after the first error', function(done) {
-      run('options/bail.fixture.js', args, function(err, res) {
+      runMochaJSON('options/bail.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -58,7 +65,10 @@ describe('options', function() {
     });
 
     it('should stop all tests after the first error in before hook', function(done) {
-      run('options/bail-with-before.fixture.js', args, function(err, res) {
+      runMochaJSON('options/bail-with-before.fixture.js', args, function(
+        err,
+        res
+      ) {
         if (err) {
           done(err);
           return;
@@ -71,7 +81,10 @@ describe('options', function() {
     });
 
     it('should stop all hooks after the first error', function(done) {
-      run('options/bail-with-after.fixture.js', args, function(err, res) {
+      runMochaJSON('options/bail-with-after.fixture.js', args, function(
+        err,
+        res
+      ) {
         if (err) {
           done(err);
           return;
@@ -90,7 +103,7 @@ describe('options', function() {
     });
 
     it('should sort tests in alphabetical order', function(done) {
-      run('options/sort*', args, function(err, res) {
+      runMochaJSON('options/sort*', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -108,7 +121,7 @@ describe('options', function() {
     it('should run tests passed via file first', function(done) {
       args = ['--file', resolvePath('options/file-alpha.fixture.js')];
 
-      run('options/file-beta.fixture.js', args, function(err, res) {
+      runMochaJSON('options/file-beta.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -128,7 +141,7 @@ describe('options', function() {
         resolvePath('options/file-beta.fixture.js')
       ];
 
-      run('options/file-theta.fixture.js', args, function(err, res) {
+      runMochaJSON('options/file-theta.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -152,7 +165,7 @@ describe('options', function() {
     });
 
     it('should run the generated test suite', function(done) {
-      run('options/delay.fixture.js', args, function(err, res) {
+      runMochaJSON('options/delay.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -163,7 +176,7 @@ describe('options', function() {
     });
 
     it('should execute exclusive tests only', function(done) {
-      run('options/delay-only.fixture.js', args, function(err, res) {
+      runMochaJSON('options/delay-only.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -180,7 +193,7 @@ describe('options', function() {
     });
 
     it('should throw an error if the test suite failed to run', function(done) {
-      run('options/delay-fail.fixture.js', args, function(err, res) {
+      runMochaJSON('options/delay-fail.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -197,7 +210,7 @@ describe('options', function() {
   describe('--grep', function() {
     it('runs specs matching a string', function(done) {
       args = ['--grep', 'match'];
-      run('options/grep.fixture.js', args, function(err, res) {
+      runMochaJSON('options/grep.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -212,7 +225,7 @@ describe('options', function() {
     describe('runs specs matching a RegExp', function() {
       it('with RegExp like strings(pattern follow by flag)', function(done) {
         args = ['--grep', '/match/i'];
-        run('options/grep.fixture.js', args, function(err, res) {
+        runMochaJSON('options/grep.fixture.js', args, function(err, res) {
           if (err) {
             done(err);
             return;
@@ -226,7 +239,7 @@ describe('options', function() {
 
       it('string as pattern', function(done) {
         args = ['--grep', '.*'];
-        run('options/grep.fixture.js', args, function(err, res) {
+        runMochaJSON('options/grep.fixture.js', args, function(err, res) {
           if (err) {
             done(err);
             return;
@@ -243,7 +256,7 @@ describe('options', function() {
     describe('with --invert', function() {
       it('runs specs that do not match the pattern', function(done) {
         args = ['--grep', 'fail', '--invert'];
-        run('options/grep.fixture.js', args, function(err, res) {
+        runMochaJSON('options/grep.fixture.js', args, function(err, res) {
           if (err) {
             done(err);
             return;
@@ -260,7 +273,7 @@ describe('options', function() {
   describe('--retries', function() {
     it('retries after a certain threshold', function(done) {
       args = ['--retries', '3'];
-      run('options/retries.fixture.js', args, function(err, res) {
+      runMochaJSON('options/retries.fixture.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -282,7 +295,7 @@ describe('options', function() {
     });
 
     it('succeeds if there are only passed tests', function(done) {
-      run('options/forbid-only/passed.js', args, function(err, res) {
+      runMochaJSON('options/forbid-only/passed.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -293,7 +306,7 @@ describe('options', function() {
     });
 
     it('fails if there are tests marked only', function(done) {
-      run('options/forbid-only/only.js', args, function(err, res) {
+      runMochaJSON('options/forbid-only/only.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
@@ -304,15 +317,83 @@ describe('options', function() {
     });
 
     it('fails if there are tests in suites marked only', function(done) {
-      run('options/forbid-only/only-suite.js', args, function(err, res) {
+      runMocha('options/forbid-only/only-suite.js', args, function(err, res) {
         if (err) {
           done(err);
           return;
         }
-        expect(res, 'to have failed with error', onlyErrorMessage);
+        expect(res, 'to satisfy', {
+          code: 1,
+          output: new RegExp(onlyErrorMessage)
+        });
+        done();
+      });
+    });
+
+    it('fails if there is empty suite marked only', function(done) {
+      runMocha('options/forbid-only/only-empty-suite.js', args, function(
+        err,
+        res
+      ) {
+        if (err) {
+          done(err);
+          return;
+        }
+        expect(res, 'to satisfy', {
+          code: 1,
+          output: new RegExp(onlyErrorMessage)
+        });
         done();
       });
     });
+
+    it('fails if there is suite marked only which matches a grep', function(done) {
+      runMocha(
+        'options/forbid-only/only-suite.js',
+        args.concat('--fgrep', 'suite marked with only'),
+        function(err, res) {
+          if (err) {
+            done(err);
+            return;
+          }
+          expect(res, 'to satisfy', {
+            code: 1,
+            output: new RegExp(onlyErrorMessage)
+          });
+          done();
+        }
+      );
+    });
+
+    it('succeeds if suite marked only does not match grep', function(done) {
+      runMochaJSON(
+        'options/forbid-only/only-suite.js',
+        args.concat('--fgrep', 'bumble bees'),
+        function(err, res) {
+          if (err) {
+            done(err);
+            return;
+          }
+          expect(res, 'to have passed');
+          done();
+        }
+      );
+    });
+
+    it('succeeds if suite marked only does not match grep (using "invert")', function(done) {
+      runMochaJSON(
+        'options/forbid-only/only-suite.js',
+        args.concat('--fgrep', 'suite marked with only', '--invert'),
+        function(err, res) {
+          if (err) {
+            done(err);
+            return;
+          }
+          expect(res, 'to have passed');
+          done();
+        }
+      );
+    });
   });
 
   describe('--forbid-pending', function() {
@@ -323,7 +404,10 @@ describe('options', function() {
     });
 
     it('succeeds if there are only passed tests', function(done) {
-      run('options/forbid-pending/passed.js', args, function(err, res) {
+      runMochaJSON('options/forbid-pending/passed.js', args, function(
+        err,
+        res
+      ) {
         if (err) {
           done(err);
           return;
@@ -344,7 +428,7 @@ describe('options', function() {
 
     Object.keys(forbidPendingFailureTests).forEach(function(title) {
       it(title, function(done) {
-        run(
+        runMochaJSON(
           path.join(
             'options',
             'forbid-pending',
@@ -386,7 +470,7 @@ describe('options', function() {
         var t;
         var args = behaviors[behavior] ? [behaviors[behavior]] : [];
 
-        var mocha = run('exit.fixture.js', args, function(err) {
+        var mocha = runMochaJSON('exit.fixture.js', args, function(err) {
           clearTimeout(t);
           if (err) {
             done(err);
@@ -447,7 +531,7 @@ describe('options', function() {
      * Calls handleResult with the result.
      */
     function runMochaTest(fixture, args, handleResult, done) {
-      run(fixture, args, function(err, res) {
+      runMochaJSON(fixture, args, function(err, res) {
         if (err) {
           done(err);
           return;