Getting invalid parameter response when creating geo_locations targeting spec in the Facebook Marketing api

_x000D_ _x000D_ I am trying to add cities to my geo_location targeting in a facebook marketing api call. $targeting_spec = array( 'geo_locations' => [ 'countries' => ['US'], 'cities' => ['key' => '2490299','radius' => 10, 'distance_unit' => 'mile'] ], 'age_min' => 13, ); My code above seems like it should be correct, especially after looking at the docs here. However I get the following error: {"error":{"message":"Invalid parameter","type":"OAuthException","code":100,"error_subcode":1487079,"is_transient":false,"error_user_title":"Invalid Targeting Spec","error_user_msg":"The specified targeting spec is not valid because: Invalid data for field geo_locations. Invalid Targeting Spec: The specified targeting spec is not valid because: Normalization expecs a KeyedTraversable. TAAL[BLAME_file]\n","fbtrace_id":"HwU9EMDTah1"}} It seems to be saying there's something invalid about my geo_locations field but I have no idea what that could be. Any ideas? Thank you.