diff --git a/ryu/topology/api.py b/ryu/topology/api.py
index 908d8de1..ed56ce78 100644
--- a/ryu/topology/api.py
+++ b/ryu/topology/api.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from ryu.base import app_manager
 from ryu.topology import event
 
 
@@ -32,3 +33,6 @@ def get_link(app, dpid=None):
 
 def get_all_link(app):
     return get_link(app)
+
+
+app_manager.require_app('ryu.topology.switches')