diff --git a/lib/saml11.js b/lib/saml11.js
index f359aa54..7156d609 100644
--- a/lib/saml11.js
+++ b/lib/saml11.js
@@ -3,8 +3,8 @@ var utils = require('./utils'),
     Parser = require('xmldom').DOMParser,
     SignedXml = require('xml-crypto').SignedXml,
     xmlenc = require('xml-encryption'),
-    moment = require('moment');
-    async = require('async');
+    moment = require('moment'),
+    async = require('async'),
     crypto = require('crypto');
 
 var fs = require('fs');
@@ -28,26 +28,24 @@ exports.create = function(options, callback) {
   if (!options.key)
     throw new Error('Expect a private key in pem format');
 
-  if (!options.cert)
-    throw new Error('Expect a public key cert in pem format');
-
   options.signatureAlgorithm = options.signatureAlgorithm || 'rsa-sha256';
   options.digestAlgorithm = options.digestAlgorithm || 'sha256';
 
-  var cert = utils.pemToCert(options.cert);
-
   var sig = new SignedXml(null, { signatureAlgorithm: algorithms.signature[options.signatureAlgorithm], idAttribute: 'AssertionID' });
   sig.addReference("//*[local-name(.)='Assertion']",
                   ["http://www.w3.org/2000/09/xmldsig#enveloped-signature", "http://www.w3.org/2001/10/xml-exc-c14n#"],
                   algorithms.digest[options.digestAlgorithm]);
 
   sig.signingKey = options.key;
-  
-  sig.keyInfoProvider = {
-    getKeyInfo: function () {
-      return "<X509Data><X509Certificate>" + cert + "</X509Certificate></X509Data>";
-    }
-  };
+
+  if (options.cert) {
+    var cert = utils.pemToCert(options.cert);
+    sig.keyInfoProvider = {
+      getKeyInfo: function () {
+        return "<X509Data><X509Certificate>" + cert + "</X509Certificate></X509Data>";
+      }
+    };
+  }
 
   var doc;
   try {
diff --git a/lib/saml20.js b/lib/saml20.js
index 21c1f278..8cf7c968 100644
--- a/lib/saml20.js
+++ b/lib/saml20.js
@@ -59,9 +59,6 @@ exports.create = function(options, callback) {
   if (!options.key)
     throw new Error('Expect a private key in pem format');
 
-  if (!options.cert)
-    throw new Error('Expect a public key cert in pem format');
-
   options.signatureAlgorithm = options.signatureAlgorithm || 'rsa-sha256';
   options.digestAlgorithm = options.digestAlgorithm || 'sha256';
 
@@ -72,21 +69,22 @@ exports.create = function(options, callback) {
   options.signatureNamespacePrefix = options.signatureNamespacePrefix || options.prefix;
   options.signatureNamespacePrefix = typeof options.signatureNamespacePrefix === 'string' ? options.signatureNamespacePrefix : '' ; 
 
-  var cert = utils.pemToCert(options.cert);
-
   var sig = new SignedXml(null, { signatureAlgorithm: algorithms.signature[options.signatureAlgorithm], idAttribute: 'ID' });
   sig.addReference("//*[local-name(.)='Assertion']",
                   ["http://www.w3.org/2000/09/xmldsig#enveloped-signature", "http://www.w3.org/2001/10/xml-exc-c14n#"],
                   algorithms.digest[options.digestAlgorithm]);
 
   sig.signingKey = options.key;
-  
-  sig.keyInfoProvider = {
-    getKeyInfo: function (key, prefix) {
-      prefix = prefix ? prefix + ':' : prefix;
-      return "<" + prefix + "X509Data><" + prefix + "X509Certificate>" + cert + "</" + prefix + "X509Certificate></" + prefix + "X509Data>";
-    }
-  };
+
+  if (options.cert) {
+    var cert = utils.pemToCert(options.cert);
+    sig.keyInfoProvider = {
+      getKeyInfo: function (key, prefix) {
+        prefix = prefix ? prefix + ':' : prefix;
+        return "<" + prefix + "X509Data><" + prefix + "X509Certificate>" + cert + "</" + prefix + "X509Certificate></" + prefix + "X509Data>";
+      }
+    };
+  }
 
   var doc;
   try {
diff --git a/package.json b/package.json
index 2eacb838..d2a1ae21 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "saml",
-  "version": "0.13.0",
+  "version": "0.13.1",
   "devDependencies": {
     "mocha": "3.5.3",
     "should": "~1.2.1"
diff --git a/test/saml11.tests.js b/test/saml11.tests.js
index d924c278..f4314122 100644
--- a/test/saml11.tests.js
+++ b/test/saml11.tests.js
@@ -22,6 +22,16 @@ describe('saml 1.1', function () {
     var isValid = utils.isValidSignature(signedAssertion, options.cert);
     assert.equal(true, isValid);
   });
+  
+  it('should ignore cert if not present', function () {
+    var options = {
+      key: fs.readFileSync(__dirname + '/test-auth0.key')
+    };
+
+    var signedAssertion = saml11.create(options);
+    var isValid = utils.isValidSignature(signedAssertion, fs.readFileSync(__dirname + '/test-auth0.pem'));
+    assert.equal(true, isValid);
+  });
 
   it('should support specifying Issuer property', function () {
     var options = {
diff --git a/test/saml20.tests.js b/test/saml20.tests.js
index e351cfa3..0487ff8b 100644
--- a/test/saml20.tests.js
+++ b/test/saml20.tests.js
@@ -56,6 +56,26 @@ describe('saml 2.0', function () {
     assert.equal('urn:oasis:names:tc:SAML:2.0:ac:classes:unspecified', authnContextClassRef.textContent);
   });
 
+  
+  it('should ignore cert if not present', function () {
+    var options = {
+      key: fs.readFileSync(__dirname + '/test-auth0.key'),
+      issuer: 'urn:issuer',
+      lifetimeInSeconds: 600,
+      audiences: 'urn:myapp',
+      attributes: {
+        'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress': 'foo@bar.com',
+        'http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name': 'Foo Bar'
+      },
+      nameIdentifier:       'foo',
+      nameIdentifierFormat: 'urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified'
+    };
+
+    var signedAssertion = saml.create(options);
+    var isValid = utils.isValidSignature(signedAssertion, fs.readFileSync(__dirname + '/test-auth0.pem'));
+    assert.equal(true, isValid);
+  });
+
   it('should set attributes', function () {
     var options = {
       cert: fs.readFileSync(__dirname + '/test-auth0.pem'),
@@ -440,7 +460,6 @@ describe('saml 2.0', function () {
     assert.equal('saml:Conditions', signature[0].previousSibling.nodeName);
   });
 
-
   it('should not include AudienceRestriction when there are no audiences', function () {
      var options = {
       cert: fs.readFileSync(__dirname + '/test-auth0.pem'),