diff --git a/app/api/tiler.py b/app/api/tiler.py
index b93fa6f5..92eafc06 100644
--- a/app/api/tiler.py
+++ b/app/api/tiler.py
@@ -25,7 +25,7 @@ from rest_framework import exceptions
 from rest_framework.response import Response
 from worker.tasks import export_raster_index
 
-ZOOM_EXTRA_LEVELS = 2
+ZOOM_EXTRA_LEVELS = 3
 
 for custom_colormap in custom_colormaps:
     colormap = colormap.register(custom_colormap)
@@ -159,7 +159,7 @@ class Metadata(TaskNestedView):
                     data.mask = mask == 0
                     expression_bloc = expr.lower().split(",")
                     stats = {
-                        f"{expression_bloc[b]}": raster_stats(data[b], percentiles=(pmin, pmax), bins=255, range=hrange)
+                        str(b + 1): raster_stats(data[b], percentiles=(pmin, pmax), bins=255, range=hrange)
                         for b in range(data.shape[0])
                     }
                     stats = {b: ImageStatistics(**s) for b, s in stats.items()}
diff --git a/app/tests/test_api_task.py b/app/tests/test_api_task.py
index e3de5ea6..e135b375 100644
--- a/app/tests/test_api_task.py
+++ b/app/tests/test_api_task.py
@@ -484,8 +484,8 @@ class TestApiTask(BootTransactionTestCase):
             for f in fields:
                 self.assertTrue(f in metadata)
 
-            self.assertEqual(metadata['minzoom'], 17 - ZOOM_EXTRA_LEVELS)
-            self.assertEqual(metadata['maxzoom'], 17 + ZOOM_EXTRA_LEVELS)
+            self.assertEqual(metadata['minzoom'], 18 - ZOOM_EXTRA_LEVELS)
+            self.assertEqual(metadata['maxzoom'], 18 + ZOOM_EXTRA_LEVELS)
 
             # Colormaps and algorithms should be empty lists
             self.assertEqual(metadata['algorithms'], [])