diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
index d6fb3e8d97c..f135125b58c 100644
--- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
+++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
@@ -1626,6 +1626,9 @@ intel_miptree_alloc_aux(struct brw_context *brw,
       aux_surf_ok =
          isl_surf_get_ccs_surf(&brw->isl_dev, &mt->surf, &aux_surf, 0);
       break;
+
+   default:
+      unreachable("Invalid aux usage");
    }
 
    /* We should have a valid aux_surf. */