diff --git a/config.yml b/config.yml
index 1dfe024..4269d06 100644
--- a/config.yml
+++ b/config.yml
@@ -1,6 +1,8 @@
 globals: {}
 grids:
-  mercator: { base: GLOBAL_MERCATOR }
+  mercator:
+    base: GLOBAL_MERCATOR
+    num_levels: 22
 services:
   demo: {}
   tms: { origin: nw, use_grid_names: true }