diff --git a/docs/03-cellxgene-census.ipynb b/docs/03-cellxgene-census.ipynb
index 2053268..b803e94 100644
--- a/docs/03-cellxgene-census.ipynb
+++ b/docs/03-cellxgene-census.ipynb
@@ -539,7 +539,7 @@
    },
    "outputs": [],
    "source": [
-    "adata_slice = adata_backed[\n",
+    "adata_backed_slice = adata_backed[\n",
     "    adata_backed.obs.cell_type.isin(\n",
     "        [cell_types.dendritic_cell.name, cell_types.neutrophil.name]\n",
     "    )\n",
@@ -548,7 +548,7 @@
     "    & (adata_backed.obs.assay == experimental_factors.ln_10x_3_v2.name)\n",
     "]\n",
     "\n",
-    "adata_slice.to_memory()"
+    "adata_backed_slice.to_memory()"
    ]
   },
   {
@@ -571,6 +571,7 @@
     "```\n",
     "adata_slices = []\n",
     "for file in query:\n",
+    "    adata_backed = file.backed()\n",
     "    adata_slice = adata_backed[\n",
     "        adata_backed.obs.cell_type.isin(\n",
     "            [cell_types.dendritic_cell.name, cell_types.neutrophil.name]\n",