diff --git a/api/blueprints/MilestoneAPI.py b/api/blueprints/MilestoneAPI.py
index d9da771abff58585e4bff4969136bb268ce05528..e161065811a0cfa966c323447ef3441bec2a7137 100644
--- a/api/blueprints/MilestoneAPI.py
+++ b/api/blueprints/MilestoneAPI.py
@@ -55,6 +55,9 @@ def construct_blueprint(database):
     @milestone_api.route('/milestones/<int:roadmapID>/latest', methods=['GET'])
     def get_latest_milestone(roadmapID):
         milestone = database.get_latest_milestone(roadmapID)
+        if milestone is None:
+            return 'No closed milestones existing for roadmap with ID "{}"'.format(roadmapID), 400
+
         return jsonify(prepare_milestone(milestone))
 
     @milestone_api.route('/milestone/<int:milestoneID>', methods=['GET'])
diff --git a/api/version.json b/api/version.json
index 0571b6fdb8fd5fe695a492fa2b6104d5997362bf..22053ff4fa2f5d5ca4f0291fba72ced400acab68 100644
--- a/api/version.json
+++ b/api/version.json
@@ -1,7 +1,7 @@
 {
     "version": {
-        "name": "v2.5.0",
-        "code": 16,
-        "date": "03.10.19"
+        "name": "v2.5.1",
+        "code": 17,
+        "date": "18.04.20"
     }
 }
\ No newline at end of file