diff --git a/nordpool/elspot.py b/nordpool/elspot.py
index 7a40329..4ae67b3 100644
--- a/nordpool/elspot.py
+++ b/nordpool/elspot.py
@@ -226,7 +226,7 @@ async def _io(self, url, params):
 
         resp = await self.client.get(url, params=params)
         # aiohttp
-        if inspect.isawaitable(resp.json()):
+        if inspect.iscoroutinefunction(resp.json):
             return await resp.json()
         # Httpx and asks
         return resp.json()