diff --git a/gns3server/controller/project.py b/gns3server/controller/project.py
index ece3d328..7d2ef53d 100644
--- a/gns3server/controller/project.py
+++ b/gns3server/controller/project.py
@@ -931,7 +931,7 @@ class Project:
                 yield from wait_run_in_executor(self._create_duplicate_project_file, project_path, zipstream)
                 with open(project_path, "rb") as f:
                     project = yield from import_project(self._controller, str(uuid.uuid4()), f, location=location, name=name, keep_compute_id=True)
-        except (OSError, UnicodeEncodeError) as e:
+        except (ValueError, OSError, UnicodeEncodeError) as e:
             raise aiohttp.web.HTTPConflict(text="Can not duplicate project: {}".format(str(e)))
 
         if previous_status == "closed":
diff --git a/gns3server/controller/udp_link.py b/gns3server/controller/udp_link.py
index 479d66b5..018ed450 100644
--- a/gns3server/controller/udp_link.py
+++ b/gns3server/controller/udp_link.py
@@ -54,7 +54,7 @@ class UDPLink(Link):
         try:
             (node1_host, node2_host) = yield from node1.compute.get_ip_on_same_subnet(node2.compute)
         except ValueError as e:
-            raise aiohttp.web.HTTPConflict(text=str(e))
+            raise aiohttp.web.HTTPConflict(text="Cannot get an IP address on same subnet: {}".format(e))
 
         # Reserve a UDP port on both side
         response = yield from node1.compute.post("/projects/{}/ports/udp".format(self._project.id))