diff --git a/examples/Carbon_Flux.ipynb b/examples/Carbon_Flux.ipynb
index 1c2b337..68cc584 100644
--- a/examples/Carbon_Flux.ipynb
+++ b/examples/Carbon_Flux.ipynb
@@ -68,9 +68,8 @@
     "    for i in range(50):\n",
     "        df = df.replace(limit - i, np.nan)\n",
     "    \n",
-    "    assert all([col in df.columns for col in drop])\n",
+    "    assert all([col in df.columns for col in drop]), \"Some columns to drop not in the dataframe.\"\n",
     "    df.drop(columns=drop, inplace=True)\n",
-    "    assert not all([col in df.columns for col in drop])\n",
     "    for col in keep:\n",
     "        if col not in df.columns:\n",
     "            if 'SWC_F' in col or 'TS_F' in col:\n",