diff --git a/index.js b/index.js
index 133e4d1..1459f88 100644
--- a/index.js
+++ b/index.js
@@ -137,7 +137,7 @@ Cookies.prototype.set = function(name, value, opts) {
 
   pushCookie(headers, cookie)
 
-  if (opts && signed) {
+  if (signed) {
     if (!this.keys) throw new Error('.keys required for signed cookies');
     cookie.value = this.keys.sign(cookie.toString())
     cookie.name += ".sig"
diff --git a/test/test.js b/test/test.js
index e6a5901..9ade3f3 100644
--- a/test/test.js
+++ b/test/test.js
@@ -496,6 +496,29 @@ describe('new Cookies(req, res, [options])', function () {
     })
 
     describe('"signed" option', function () {
+      describe('when omitted', function () {
+        it('should default to signed when .keys are present', function (done) {
+          var opts = { keys: ['keyboard cat'] }
+
+          request(createServer(opts, setCookieHandler('foo', 'bar')))
+            .get('/')
+            .expect(200)
+            .expect(shouldSetCookieCount(2))
+            .expect(shouldSetCookieToValue('foo', 'bar'))
+            .expect(shouldSetCookieToValue('foo.sig', 'iW2fuCIzk9Cg_rqLT1CAqrtdWs8'))
+            .end(done)
+        })
+
+        it('should not set additional .sig cookie when .keys are not present', function (done) {
+          request(createServer(setCookieHandler('foo', 'bar')))
+            .get('/')
+            .expect(200)
+            .expect(shouldSetCookieCount(1))
+            .expect(shouldSetCookieToValue('foo', 'bar'))
+            .end(done)
+        })
+      })
+
       describe('when true', function () {
         it('should throw without .keys', function (done) {
           request(createServer(setCookieHandler('foo', 'bar', { signed: true })))