diff --git a/test/validators.js b/test/validators.js
index 251103043..b835cf860 100644
--- a/test/validators.js
+++ b/test/validators.js
@@ -1425,7 +1425,13 @@ describe('Validators', function () {
         test({
             validator: 'isBase64'
           , valid: [
-                'TG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyIGFkaXBpc2NpbmcgZWxpdC4='
+                'Zg=='
+              , 'Zm8='
+              , 'Zm9v'
+              , 'Zm9vYg=='
+              , 'Zm9vYmE='
+              , 'Zm9vYmFy'
+              , 'TG9yZW0gaXBzdW0gZG9sb3Igc2l0IGFtZXQsIGNvbnNlY3RldHVyIGFkaXBpc2NpbmcgZWxpdC4='
               , 'Vml2YW11cyBmZXJtZW50dW0gc2VtcGVyIHBvcnRhLg=='
               , 'U3VzcGVuZGlzc2UgbGVjdHVzIGxlbw=='
               , 'MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAuMPNS1Ufof9EW/M98FNw'+
@@ -1440,6 +1446,11 @@ describe('Validators', function () {
                 '12345'
               , ''
               , 'Vml2YW11cyBmZXJtZtesting123'
+              , 'Zg='
+              , 'Z==='
+              , 'Zm=8'
+              , '=m9vYg=='
+              , 'Zm9vYmFy===='
             ]
         });
         for (var i = 0, str = '', encoded; i < 1000; i++) {
diff --git a/validator.js b/validator.js
index dcc9e4599..f1e9a7753 100644
--- a/validator.js
+++ b/validator.js
@@ -104,7 +104,7 @@
 
     var surrogatePair = /[\uD800-\uDBFF][\uDC00-\uDFFF]/;
 
-    var base64 = /^(?:[A-Z0-9+\/]{4})*(?:[A-Z0-9+\/]{2}==|[A-Z0-9+\/]{3}=|[A-Z0-9+\/]{4})$/i;
+    var notBase64 = /[^A-Z0-9+\/=]/i;
 
     var phones = {
       'en-US': /^(\+?1)?[2-9]\d{2}[2-9](?!11)\d{6}$/,
@@ -834,7 +834,14 @@
     };
 
     validator.isBase64 = function (str) {
-        return base64.test(str);
+        var len = str.length;
+        if (!len || len % 4 !== 0 || notBase64.test(str)) {
+            return false;
+        }
+        var firstPaddingChar = str.indexOf('=');
+        return firstPaddingChar === -1 ||
+            firstPaddingChar === len - 1 ||
+            (firstPaddingChar === len - 2 && str[len - 1] === '=');
     };
 
     validator.isMongoId = function (str) {