diff --git a/sources/02e Spectral Indices.ipynb b/sources/02e Spectral Indices.ipynb
index ed6afd8..a7d4abb 100644
--- a/sources/02e Spectral Indices.ipynb	
+++ b/sources/02e Spectral Indices.ipynb	
@@ -157,7 +157,7 @@
     "    # normalized difference in vegetation\n",
     "    'ndvi': (div, (sub, 'B08', 'B04'), (add, 'B08', 'B04')),\n",
     "    # normalized difference in water index\n",
-    "    'ndwi': (div (sub, 'B03', 'B08'), (add, 'B03', 'B08')),\n",
+    "    'ndwi': (div, (sub, 'B03', 'B08'), (add, 'B03', 'B08')),\n",
     "    # bare soil index\n",
     "    'bsi': (div, (sub, (add, 'B11', 'B04'), (add, 'B08', 'B02')),\n",
     "                 (add, (add, 'B11', 'B04'), (add, 'B08', 'B02')))\n",