diff --git a/homematicip/aio/group.py b/homematicip/aio/group.py
index 8c1084e5..568b5eb6 100644
--- a/homematicip/aio/group.py
+++ b/homematicip/aio/group.py
@@ -120,8 +120,8 @@ async def set_shutter_stop(self):
         url, data = super().set_shutter_stop()
         return await self._connection.api_call(url, data)
 
-    async def set_slats_level(self, slatsLevel, shutterlevel):
-        url, data = super().set_slats_level(slatsLevel, shutterlevel)
+    async def set_slats_level(self, slatsLevel=0.0, shutterLevel=None):
+        url, data = super().set_slats_level(slatsLevel, shutterLevel)
         return await self._connection.api_call(url, data)
 
 
diff --git a/homematicip/group.py b/homematicip/group.py
index f16b25a7..2d6f1091 100644
--- a/homematicip/group.py
+++ b/homematicip/group.py
@@ -340,10 +340,10 @@ def set_shutter_level(self, level):
         data = {"groupId": self.id, "shutterLevel": level}
         return self._restCall("group/switching/setShutterLevel", body=json.dumps(data))
 
-    def set_slats_level(self, slatsLevel, shutterlevel):
+    def set_slats_level(self, slatsLevel=0.0, shutterLevel=None):
         data = {
             "groupId": self.id,
-            "shutterLevel": shutterlevel,
+            "shutterLevel": shutterLevel,
             "slatsLevel": slatsLevel,
         }
         return self._restCall("group/switching/setSlatsLevel", body=json.dumps(data))