diff --git a/sanic/exceptions.py b/sanic/exceptions.py
index 0133fd64..6da747f2 100644
--- a/sanic/exceptions.py
+++ b/sanic/exceptions.py
@@ -263,7 +263,7 @@ class Unauthorized(SanicException):
 
         # if auth-scheme is specified, set "WWW-Authenticate" header
         if scheme is not None:
-            values = ["{!s}={!r}".format(k, v) for k, v in kwargs.items()]
+            values = ['{!s}="{!s}"'.format(k, v) for k, v in kwargs.items()]
             challenge = ', '.join(values)
 
             self.headers = {
diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py
index 16d08459..b4e2c6ea 100644
--- a/tests/test_exceptions.py
+++ b/tests/test_exceptions.py
@@ -138,7 +138,7 @@ def test_unauthorized_exception(exception_app):
     request, response = exception_app.test_client.get('/401/basic')
     assert response.status == 401
     assert response.headers.get('WWW-Authenticate') is not None
-    assert response.headers.get('WWW-Authenticate') == "Basic realm='Sanic'"
+    assert response.headers.get('WWW-Authenticate') == 'Basic realm="Sanic"'
 
     request, response = exception_app.test_client.get('/401/digest')
     assert response.status == 401
@@ -146,10 +146,10 @@ def test_unauthorized_exception(exception_app):
     auth_header = response.headers.get('WWW-Authenticate')
     assert auth_header is not None
     assert auth_header.startswith('Digest')
-    assert "qop='auth, auth-int'" in auth_header
-    assert "algorithm='MD5'" in auth_header
-    assert "nonce='abcdef'" in auth_header
-    assert "opaque='zyxwvu'" in auth_header
+    assert 'qop="auth, auth-int"' in auth_header
+    assert 'algorithm="MD5"' in auth_header
+    assert 'nonce="abcdef"' in auth_header
+    assert 'opaque="zyxwvu"' in auth_header
 
     request, response = exception_app.test_client.get('/401/bearer')
     assert response.status == 401