diff --git a/gns3server/controller/project.py b/gns3server/controller/project.py
index 507dc4b3..b9f053c7 100644
--- a/gns3server/controller/project.py
+++ b/gns3server/controller/project.py
@@ -439,6 +439,12 @@ class Project:
         :returns: ZipStream object
         """
         z = zipstream.ZipFile()
+
+        # First we process the .gns3 in order to be sure we don't have an error
+        for file in os.listdir(self._path):
+            if file.endswith(".gns3"):
+                self._export_project_file(os.path.join(self._path, file), z, include_images)
+
         for root, dirs, files in os.walk(self._path, topdown=True):
             # Remove snapshots and capture
             if os.path.split(root)[-1:][0] == "project-files":
@@ -457,9 +463,8 @@ class Project:
                     log.warn(msg)
                     self.emit("log.warning", {"message": msg})
                     continue
-            # We rename the .gns3 project.gns3 to avoid the task to the client to guess the file name
             if file.endswith(".gns3"):
-                self._export_project_file(path, z, include_images)
+                pass
             else:
                 z.write(path, os.path.relpath(path, self._path), compress_type=zipfile.ZIP_DEFLATED)
         return z
@@ -468,6 +473,8 @@ class Project:
         """
         Take a project file (.gns3) and patch it for the export
 
+        We rename the .gns3 project.gns3 to avoid the task to the client to guess the file name
+
         :param path: Path of the .gns3
         """
 
@@ -478,12 +485,15 @@ class Project:
             topology = json.load(f)
         if "topology" in topology and "nodes" in topology["topology"]:
             for node in topology["topology"]["nodes"]:
+                if node["node_type"] in ["virtualbox", "vmware", "cloud"]:
+                    raise aiohttp.web.HTTPConflict(text="Topology with a {} could not be exported".format(node["node_type"]))
+
                 if "properties" in node and node["node_type"] != "Docker":
                     for prop, value in node["properties"].items():
                         if prop.endswith("image"):
                             node["properties"][prop] = os.path.basename(value)
                             if include_images is True:
-                                images.append(value)
+                                images.add(value)
 
         for image in images:
             self._export_images(image, z)
diff --git a/gns3server/handlers/api/controller/project_handler.py b/gns3server/handlers/api/controller/project_handler.py
index fffdcacc..c6baf615 100644
--- a/gns3server/handlers/api/controller/project_handler.py
+++ b/gns3server/handlers/api/controller/project_handler.py
@@ -231,14 +231,21 @@ class ProjectHandler:
         controller = Controller.instance()
         project = controller.get_project(request.match_info["project_id"])
 
-        response.content_type = 'application/gns3project'
-        response.headers['CONTENT-DISPOSITION'] = 'attachment; filename="{}.gns3project"'.format(project.name)
-        response.enable_chunked_encoding()
-        # Very important: do not send a content length otherwise QT closes the connection (curl can consume the feed)
-        response.content_length = None
-        response.start(request)
+
+        started = False
 
         for data in project.export(include_images=bool(request.GET.get("include_images", "0"))):
+            # We need to do that now because export could failed and raise an HTTP error
+            # that why response start need to be the later possible
+            if not started:
+                response.content_type = 'application/gns3project'
+                response.headers['CONTENT-DISPOSITION'] = 'attachment; filename="{}.gns3project"'.format(project.name)
+                response.enable_chunked_encoding()
+                # Very important: do not send a content length otherwise QT closes the connection (curl can consume the feed)
+                response.content_length = None
+                response.start(request)
+                started = True
+
             response.write(data)
             yield from response.drain()
 
diff --git a/tests/controller/test_project.py b/tests/controller/test_project.py
index 71136e1d..21694660 100644
--- a/tests/controller/test_project.py
+++ b/tests/controller/test_project.py
@@ -351,6 +351,30 @@ def test_export(tmpdir, project):
         assert 'vm-1/dynamips/test_log.txt' not in myzip.namelist()
 
 
+def test_export_disallow_some_type(tmpdir, project):
+    """
+    Fix absolute image path
+    """
+
+    path = project.path
+
+    topology = {
+        "topology": {
+            "nodes": [
+                    {
+                        "node_type": "virtualbox"
+                    }
+            ]
+        }
+    }
+
+    with open(os.path.join(path, "test.gns3"), 'w+') as f:
+        json.dump(topology, f)
+
+    with pytest.raises(aiohttp.web.HTTPConflict):
+        z = project.export()
+
+
 def test_export_fix_path(tmpdir, project):
     """
     Fix absolute image path