diff --git a/backend/right_tree/api/filters.py b/backend/right_tree/api/filters.py
index 28ad173..f7bf4f4 100644
--- a/backend/right_tree/api/filters.py
+++ b/backend/right_tree/api/filters.py
@@ -38,8 +38,12 @@ def soil_variant_filter(request, queryset):
 
 def zone_filter(request, queryset):
     zone = request.query_params.get('zone')
-    zone_json = json.loads(zone)
-    return queryset.filter(zones__id__contains=zone_json['id']).distinct()
+
+    if zone != None:
+        zone_json = json.loads(zone)
+        return queryset.filter(zones__id__contains=zone_json['id']).distinct()
+
+    return queryset
 
 
 def soil_order_coordinate_filter(coordinates):