diff --git a/flask/app.py b/flask/app.py
index 1d2e356c..a837c030 100644
--- a/flask/app.py
+++ b/flask/app.py
@@ -949,6 +949,9 @@ class Flask(_PackageBoundObject):
         # a tuple of only `GET` as default.
         if methods is None:
             methods = getattr(view_func, 'methods', None) or ('GET',)
+        if isinstance(methods, string_types):
+            raise TypeError('Allowed methods have to be iterables of strings, '
+                            'for example: @app.route(..., methods=["POST"])')
         methods = set(methods)
 
         # Methods that should always be added
diff --git a/flask/testsuite/basic.py b/flask/testsuite/basic.py
index d95a4c37..71a1f832 100644
--- a/flask/testsuite/basic.py
+++ b/flask/testsuite/basic.py
@@ -85,6 +85,13 @@ class BasicFunctionalityTestCase(FlaskTestCase):
         self.assert_equal(rv.status_code, 405)
         self.assert_equal(sorted(rv.allow), ['GET', 'HEAD', 'OPTIONS', 'POST'])
 
+    def test_disallow_string_for_allowed_methods(self):
+        app = flask.Flask(__name__)
+        with self.assert_raises(TypeError):
+            @app.route('/', methods='GET POST')
+            def index():
+                return "Hey"
+
     def test_url_mapping(self):
         app = flask.Flask(__name__)
         def index():