diff --git a/test/verify.tests.js b/test/verify.tests.js
index 88500756..3243e306 100644
--- a/test/verify.tests.js
+++ b/test/verify.tests.js
@@ -248,6 +248,61 @@ describe('verify', function() {
       });
     });
 
+    describe('option: clockTolerance', function () {
+      const clockTimestamp = 1000000000;
+
+      it('should reject a non-number clockTolerance', function (done) {
+        const token = jwt.sign({foo: 'bar', iat: clockTimestamp, exp: clockTimestamp + 1}, key);
+        jwt.verify(token, key, {clockTolerance: '5'}, function (err, p) {
+          assert.equal(err.name, 'JsonWebTokenError');
+          assert.equal(err.message, 'clockTolerance must be a non-negative number');
+          assert.isUndefined(p);
+          done();
+        });
+      });
+
+      it('should reject a negative clockTolerance', function (done) {
+        const token = jwt.sign({foo: 'bar', iat: clockTimestamp, exp: clockTimestamp + 1}, key);
+        jwt.verify(token, key, {clockTolerance: -5}, function (err, p) {
+          assert.equal(err.name, 'JsonWebTokenError');
+          assert.equal(err.message, 'clockTolerance must be a non-negative number');
+          assert.isUndefined(p);
+          done();
+        });
+      });
+
+      it('should reject a non-finite clockTolerance', function (done) {
+        const token = jwt.sign({foo: 'bar', iat: clockTimestamp, exp: clockTimestamp + 1}, key);
+        jwt.verify(token, key, {clockTolerance: Infinity}, function (err, p) {
+          assert.equal(err.name, 'JsonWebTokenError');
+          assert.equal(err.message, 'clockTolerance must be a non-negative number');
+          assert.isUndefined(p);
+          done();
+        });
+      });
+
+      it('should reject an expired token instead of silently accepting it when clockTolerance is non-finite', function (done) {
+        // exp + Infinity === Infinity made `clockTimestamp >= exp + clockTolerance`
+        // always false, silently accepting an expired token. It is now rejected.
+        const token = jwt.sign({foo: 'bar', iat: clockTimestamp, exp: clockTimestamp - 1}, key);
+        jwt.verify(token, key, {clockTimestamp: clockTimestamp, clockTolerance: Infinity}, function (err, p) {
+          assert.equal(err.name, 'JsonWebTokenError');
+          assert.equal(err.message, 'clockTolerance must be a non-negative number');
+          assert.isUndefined(p);
+          done();
+        });
+      });
+
+      it('should accept a valid non-negative clockTolerance', function (done) {
+        const token = jwt.sign({foo: 'bar', iat: clockTimestamp, exp: clockTimestamp - 1}, key);
+        jwt.verify(token, key, {clockTimestamp: clockTimestamp, clockTolerance: 5}, function (err, p) {
+          assert.isNull(err);
+          assert.equal(p.foo, 'bar');
+          done();
+        });
+      });
+    });
+
     describe('option: maxAge and clockTimestamp', function () {
       // { foo: 'bar', iat: 1437018582, exp: 1437018800 } exp = iat + 218s
       const token = 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIiLCJpYXQiOjE0MzcwMTg1ODIsImV4cCI6MTQzNzAxODgwMH0.AVOsNC7TiT-XVSpCpkwB1240izzCIJ33Lp07gjnXVpA';
diff --git a/verify.js b/verify.js
index cdbfdc45..d46982f3 100644
--- a/verify.js
+++ b/verify.js
@@ -46,6 +46,11 @@ module.exports = function (jwtString, secretOrPublicKey, options, callback) {
     return done(new JsonWebTokenError('clockTimestamp must be a number'));
   }
 
+  if (options.clockTolerance !== undefined &&
+      (typeof options.clockTolerance !== 'number' || !Number.isFinite(options.clockTolerance) || options.clockTolerance < 0)) {
+    return done(new JsonWebTokenError('clockTolerance must be a non-negative number'));
+  }
+
   if (options.nonce !== undefined && (typeof options.nonce !== 'string' || options.nonce.trim() === '')) {
     return done(new JsonWebTokenError('nonce must be a non-empty string'));
   }