diff --git a/flask/blueprints.py b/flask/blueprints.py
index 0a6ccfb7..8311e580 100644
--- a/flask/blueprints.py
+++ b/flask/blueprints.py
@@ -49,12 +49,10 @@ class BlueprintSetupState(object):
         url_prefix = self.options.get('url_prefix')
         if url_prefix is None:
             url_prefix = self.blueprint.url_prefix
-
+        if url_prefix:
+            url_prefix = url_prefix.rstrip('/')
         #: The prefix that should be used for all URLs defined on the
         #: blueprint.
-        if url_prefix and url_prefix[-1] == '/':
-            url_prefix = url_prefix[:-1]
-
         self.url_prefix = url_prefix
 
         #: A dictionary with URL defaults that is added to each and every
@@ -68,7 +66,7 @@ class BlueprintSetupState(object):
         blueprint's name.
         """
         if self.url_prefix:
-            rule = self.url_prefix + rule
+            rule = '/'.join((self.url_prefix, rule.lstrip('/')))
         options.setdefault('subdomain', self.subdomain)
         if endpoint is None:
             endpoint = _endpoint_from_view_func(view_func)
diff --git a/tests/test_blueprints.py b/tests/test_blueprints.py
index a2631241..46364cab 100644
--- a/tests/test_blueprints.py
+++ b/tests/test_blueprints.py
@@ -115,17 +115,22 @@ def test_blueprint_app_error_handling(app, client):
     assert client.get('/nope').data == b'you shall not pass'
 
 
-def test_blueprint_prefix_slash(app, client):
-    bp = flask.Blueprint('test', __name__, url_prefix='/bar/')
-
-    @bp.route('/foo')
-    def foo():
+@pytest.mark.parametrize(('prefix', 'rule', 'url'), (
+    ('/foo/', '/bar', '/foo/bar'),
+    ('/foo/', 'bar', '/foo/bar'),
+    ('/foo', '/bar', '/foo/bar'),
+    ('/foo/', '//bar', '/foo/bar'),
+    ('/foo//', '/bar', '/foo/bar'),
+))
+def test_blueprint_prefix_slash(app, client, prefix, rule, url):
+    bp = flask.Blueprint('test', __name__, url_prefix=prefix)
+
+    @bp.route(rule)
+    def index():
         return '', 204
 
     app.register_blueprint(bp)
-    app.register_blueprint(bp, url_prefix='/spam/')
-    assert client.get('/bar/foo').status_code == 204
-    assert client.get('/spam/foo').status_code == 204
+    assert client.get(url).status_code == 204
 
 
 def test_blueprint_url_defaults(app, client):