diff --git a/src/helpers/validate.js b/src/helpers/validate.js
index c19cd752c..89e5db677 100644
--- a/src/helpers/validate.js
+++ b/src/helpers/validate.js
@@ -9,7 +9,7 @@ function validateURL (url) {
 }
 
 function validateFlags (flags) {
-  const mask = /^[\w,]+$/
+  const mask = /^(?!-)[\w,-]+$/
   return mask.test(flags)
 }
 
diff --git a/test/helpers/validate.test.js b/test/helpers/validate.test.js
index ef3e4ae40..72c41d15e 100644
--- a/test/helpers/validate.test.js
+++ b/test/helpers/validate.test.js
@@ -11,8 +11,16 @@ describe('Input Validators', function () {
   })
 
   describe('Flags', function () {
-    it('Should fail with a dash', function () {
-      expect(validate.validateFlags('moo-foor')).toBe(false)
+
+    it('Should pass without a dash', function () {
+      expect(validate.validateFlags('moo')).toBe(true)
+    })
+    it('Should pass with a dash', function () {
+      expect(validate.validateFlags('moo-foor')).toBe(true)
+    })
+
+    it('Should fail with a dash at the start', function () {
+      expect(validate.validateFlags('-moo-foor')).toBe(false)
     })
   })
 
diff --git a/test/index.test.js b/test/index.test.js
index 082e26757..d523060ef 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -47,6 +47,28 @@ describe('Uploader Core', function () {
     expect(result).toEqual({ status: 'success', resultURL: 'https://results.codecov.io' })
   }, 30000)
 
+  describe('Flags', () => {
+    it('can upload with flags', async () => {
+      process.env.CI = 'true'
+      process.env.CIRCLECI = 'true'
+
+      nock('https://codecov.io')
+        .post('/upload/v4')
+        .query(actualQueryObject => actualQueryObject.flags === 'a-flag')
+        .reply(200, 'https://results.codecov.io\nhttps://codecov.io')
+
+      nock('https://codecov.io')
+        .put('/')
+        .reply(200, 'success')
+
+      const result = await app.main({
+        flags: 'a-flag',
+        token: 'abcdefg',
+        url: 'https://codecov.io'
+      })
+      expect(result).toEqual({ status: 'success', resultURL: 'https://results.codecov.io' })
+    }, 30000)
+  })
   it('Can upload with parent sha', async function () {
     process.env.CI = 'true'
     process.env.CIRCLECI = 'true'