diff --git a/python3/vimspector/debug_session.py b/python3/vimspector/debug_session.py
index 64d14df..08e58ef 100644
--- a/python3/vimspector/debug_session.py
+++ b/python3/vimspector/debug_session.py
@@ -61,7 +61,7 @@ class DebugSession( object ):
     self._configuration = None
     self._init_complete = False
     self._launch_complete = False
-    self._on_init_complete_handlers = None
+    self._on_init_complete_handlers = []
     self._server_capabilities = {}
 
   def Start( self, launch_variables = {} ):
@@ -671,8 +671,7 @@ class DebugSession( object ):
     if self._launch_complete and self._init_complete:
       for h in self._on_init_complete_handlers:
         h()
-
-      self._on_init_complete_handlers = None
+      self._on_init_complete_handlers = []
 
       self._stackTraceView.LoadThreads( True )
 
diff --git a/support/test/python/simple_python/.vimspector.json b/support/test/python/simple_python/.vimspector.json
new file mode 100644
index 0000000..13e996c
--- /dev/null
+++ b/support/test/python/simple_python/.vimspector.json
@@ -0,0 +1,15 @@
+{
+  "configurations": {
+    "run": {
+      "adapter": "vscode-python",
+      "configuration": {
+        "request": "launch",
+        "type": "python",
+        "cwd": "${workspaceRoot}",
+        "program": "${file}",
+        "stopOnEntry": true,
+        "console": "integratedTerminal"
+      }
+    }
+  }
+}