diff --git a/web_server.py b/web_server.py
index 7354180..a429e72 100644
--- a/web_server.py
+++ b/web_server.py
@@ -28,8 +28,11 @@ class CommandRequest(BaseModel):
 
 @app.post("/command")
 async def command(req: CommandRequest):
-    response = await process(req.text)
-    return {"response": response}
+    try:
+        response = await process(req.text)
+        return {"response": response}
+    except Exception as e:
+        return JSONResponse(status_code=500, content={"response": f"Erreur : {e}"})
 
 
 @app.get("/status")
diff --git a/wireclaw_core.py b/wireclaw_core.py
index abafb63..8e44a00 100644
--- a/wireclaw_core.py
+++ b/wireclaw_core.py
@@ -96,7 +96,7 @@ async def interpret_command(text):
 async def execute_command(drone, cmd):
     global drone_armed
     action = cmd.get("action")
-    alt    = float(cmd.get("altitude", 15))
+    alt    = float(cmd.get("altitude") or 15)
     msg    = cmd.get("message", "OK")
 
     if action == "position":