diff --git a/eland/Untitled-1.ipynb b/eland/Untitled-1.ipynb
new file mode 100644
index 00000000..103c02fc
--- /dev/null
+++ b/eland/Untitled-1.ipynb
@@ -0,0 +1,369 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%load_ext autoreload\n",
+    "%autoreload 2"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import pandas as pd\n",
+    "\n",
+    "from datetime import datetime, timedelta\n",
+    "\n",
+    "dt = datetime.utcnow()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 22,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "df1 = pd.DataFrame(\n",
+    "    {\n",
+    "        \"a\": [1, 2, 3],\n",
+    "        \"b\": [1.0, 2.0, 3.0],\n",
+    "        \"c\": [\"A\", \"B\", \"C\"],\n",
+    "        \"d\": [dt, dt + timedelta(1), dt + timedelta(2)],\n",
+    "    },\n",
+    "    index=[\"0\", \"1\", \"2\"],\n",
+    ")\n",
+    "\n",
+    "df2 = pd.DataFrame({\"Z\": [3, 2, 1], \"a\": [4, 5, 6]}, index=[\"0\", \"1\", \"2\"])\n",
+    "es_index = \"test3\""
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 23,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from elasticsearch import Elasticsearch\n",
+    "\n",
+    "es_client = Elasticsearch(\"http://localhost:9200\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 24,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import eland as ed"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 25,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/sidhuas/.pyenv/versions/3.9.1/envs/eland/lib/python3.9/site-packages/elasticsearch/connection/base.py:200: ElasticsearchWarning: Elasticsearch built-in security features are not enabled. Without authentication, your cluster could be accessible to anyone. See https://www.elastic.co/guide/en/elasticsearch/reference/7.16/security-minimal-setup.html to enable security.\n",
+      "  warnings.warn(message, category=ElasticsearchWarning)\n"
+     ]
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
+       "        vertical-align: middle;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe tbody tr th {\n",
+       "        vertical-align: top;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe thead th {\n",
+       "        text-align: right;\n",
+       "    }\n",
+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>a</th>\n",
+       "      <th>b</th>\n",
+       "      <th>c</th>\n",
+       "      <th>d</th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>\n",
+       "<p>0 rows × 4 columns</p>"
+      ],
+      "text/plain": [
+       "Empty DataFrame\n",
+       "Columns: [a, b, c, d]\n",
+       "Index: []\n",
+       "\n",
+       "[0 rows x 4 columns]"
+      ]
+     },
+     "execution_count": 25,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "ed.pandas_to_eland(df1, es_client, es_index, es_dropna=True, \n",
+    "                               es_if_exists='append', use_pandas_index_for_es_ids=False)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 26,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/sidhuas/.pyenv/versions/3.9.1/envs/eland/lib/python3.9/site-packages/elasticsearch/connection/base.py:200: ElasticsearchWarning: Elasticsearch built-in security features are not enabled. Without authentication, your cluster could be accessible to anyone. See https://www.elastic.co/guide/en/elasticsearch/reference/7.16/security-minimal-setup.html to enable security.\n",
+      "  warnings.warn(message, category=ElasticsearchWarning)\n"
+     ]
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
+       "        vertical-align: middle;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe tbody tr th {\n",
+       "        vertical-align: top;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe thead th {\n",
+       "        text-align: right;\n",
+       "    }\n",
+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>Z</th>\n",
+       "      <th>a</th>\n",
+       "      <th>b</th>\n",
+       "      <th>c</th>\n",
+       "      <th>d</th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>6KaKA34BeVG4RuLOG_yX</th>\n",
+       "      <td>NaN</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.0</td>\n",
+       "      <td>A</td>\n",
+       "      <td>2021-12-29 00:13:36.956031</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6aaKA34BeVG4RuLOG_yX</th>\n",
+       "      <td>NaN</td>\n",
+       "      <td>2</td>\n",
+       "      <td>2.0</td>\n",
+       "      <td>B</td>\n",
+       "      <td>2021-12-30 00:13:36.956031</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6qaKA34BeVG4RuLOG_yX</th>\n",
+       "      <td>NaN</td>\n",
+       "      <td>3</td>\n",
+       "      <td>3.0</td>\n",
+       "      <td>C</td>\n",
+       "      <td>2021-12-31 00:13:36.956031</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>\n",
+       "<p>3 rows × 5 columns</p>"
+      ],
+      "text/plain": [
+       "                       Z  a    b  c                          d\n",
+       "6KaKA34BeVG4RuLOG_yX NaN  1  1.0  A 2021-12-29 00:13:36.956031\n",
+       "6aaKA34BeVG4RuLOG_yX NaN  2  2.0  B 2021-12-30 00:13:36.956031\n",
+       "6qaKA34BeVG4RuLOG_yX NaN  3  3.0  C 2021-12-31 00:13:36.956031\n",
+       "\n",
+       "[3 rows x 5 columns]"
+      ]
+     },
+     "execution_count": 26,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "ed.pandas_to_eland(df2, es_client, es_index, es_dropna=True, enforce_index_schema=False,\n",
+    "                               es_if_exists='append', use_pandas_index_for_es_ids=False)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 27,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/sidhuas/.pyenv/versions/3.9.1/envs/eland/lib/python3.9/site-packages/elasticsearch/connection/base.py:200: ElasticsearchWarning: Elasticsearch built-in security features are not enabled. Without authentication, your cluster could be accessible to anyone. See https://www.elastic.co/guide/en/elasticsearch/reference/7.16/security-minimal-setup.html to enable security.\n",
+      "  warnings.warn(message, category=ElasticsearchWarning)\n"
+     ]
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
+       "        vertical-align: middle;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe tbody tr th {\n",
+       "        vertical-align: top;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe thead th {\n",
+       "        text-align: right;\n",
+       "    }\n",
+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>Z</th>\n",
+       "      <th>a</th>\n",
+       "      <th>b</th>\n",
+       "      <th>c</th>\n",
+       "      <th>d</th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>6KaKA34BeVG4RuLOG_yX</th>\n",
+       "      <td>NaN</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.0</td>\n",
+       "      <td>A</td>\n",
+       "      <td>2021-12-29 00:13:36.956031</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6aaKA34BeVG4RuLOG_yX</th>\n",
+       "      <td>NaN</td>\n",
+       "      <td>2</td>\n",
+       "      <td>2.0</td>\n",
+       "      <td>B</td>\n",
+       "      <td>2021-12-30 00:13:36.956031</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6qaKA34BeVG4RuLOG_yX</th>\n",
+       "      <td>NaN</td>\n",
+       "      <td>3</td>\n",
+       "      <td>3.0</td>\n",
+       "      <td>C</td>\n",
+       "      <td>2021-12-31 00:13:36.956031</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>66aKA34BeVG4RuLOH_xK</th>\n",
+       "      <td>3.0</td>\n",
+       "      <td>4</td>\n",
+       "      <td>NaN</td>\n",
+       "      <td>NaN</td>\n",
+       "      <td>NaT</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>7KaKA34BeVG4RuLOH_xK</th>\n",
+       "      <td>2.0</td>\n",
+       "      <td>5</td>\n",
+       "      <td>NaN</td>\n",
+       "      <td>NaN</td>\n",
+       "      <td>NaT</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>7aaKA34BeVG4RuLOH_xK</th>\n",
+       "      <td>1.0</td>\n",
+       "      <td>6</td>\n",
+       "      <td>NaN</td>\n",
+       "      <td>NaN</td>\n",
+       "      <td>NaT</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>\n",
+       "<p>6 rows × 5 columns</p>"
+      ],
+      "text/plain": [
+       "                        Z  a    b    c                          d\n",
+       "6KaKA34BeVG4RuLOG_yX  NaN  1  1.0    A 2021-12-29 00:13:36.956031\n",
+       "6aaKA34BeVG4RuLOG_yX  NaN  2  2.0    B 2021-12-30 00:13:36.956031\n",
+       "6qaKA34BeVG4RuLOG_yX  NaN  3  3.0    C 2021-12-31 00:13:36.956031\n",
+       "66aKA34BeVG4RuLOH_xK  3.0  4  NaN  NaN                        NaT\n",
+       "7KaKA34BeVG4RuLOH_xK  2.0  5  NaN  NaN                        NaT\n",
+       "7aaKA34BeVG4RuLOH_xK  1.0  6  NaN  NaN                        NaT\n",
+       "\n",
+       "[6 rows x 5 columns]"
+      ]
+     },
+     "execution_count": 27,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "ed.DataFrame(es_client, es_index)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "interpreter": {
+   "hash": "a4e377a64fa06eb866bfeb92d02adfe8420325b7057dd732fb302fa0a637b068"
+  },
+  "kernelspec": {
+   "display_name": "Python 3.9.1 64-bit ('eland': pyenv)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.9.1"
+  },
+  "orig_nbformat": 4
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}
diff --git a/eland/etl.py b/eland/etl.py
index 3a604521..4ef11817 100644
--- a/eland/etl.py
+++ b/eland/etl.py
@@ -48,6 +48,7 @@ def pandas_to_eland(
     es_refresh: bool = False,
     es_dropna: bool = False,
     es_type_overrides: Optional[Mapping[str, str]] = None,
+    enforce_index_schema: bool = True,
     thread_count: int = 4,
     chunksize: Optional[int] = None,
     use_pandas_index_for_es_ids: bool = True,
@@ -177,7 +178,7 @@ def pandas_to_eland(
             es_client.indices.delete(index=es_dest_index)
             es_api_compat(es_client.indices.create, index=es_dest_index, body=mapping)
 
-        elif es_if_exists == "append":
+        elif es_if_exists == "append" and enforce_index_schema:
             dest_mapping = es_client.indices.get_mapping(index=es_dest_index)[
                 es_dest_index
             ]
diff --git a/tests/etl/test_pandas_to_eland.py b/tests/etl/test_pandas_to_eland.py
index c99f57c3..155029d8 100644
--- a/tests/etl/test_pandas_to_eland.py
+++ b/tests/etl/test_pandas_to_eland.py
@@ -137,7 +137,7 @@ def test_es_if_exists_append(self):
         pd_df3 = pd_df.append(pd_df2)
         assert_pandas_eland_frame_equal(pd_df3, df2)
 
-    def test_es_if_exists_append_mapping_mismatch(self):
+    def test_es_if_exists_append_mapping_mismatch_schema_enforcement(self):
         df1 = pandas_to_eland(
             pd_df,
             es_client=ES_TEST_CLIENT,
@@ -154,14 +154,29 @@ def test_es_if_exists_append_mapping_mismatch(self):
                 es_if_exists="append",
             )
 
-        assert str(e.value) == (
-            "DataFrame dtypes and Elasticsearch index mapping aren't compatible:\n"
-            "- 'b' is missing from DataFrame columns\n"
-            "- 'c' is missing from DataFrame columns\n"
-            "- 'd' is missing from DataFrame columns\n"
-            "- 'Z' is missing from ES index mapping\n"
-            "- 'a' column type ('keyword') not compatible with ES index mapping type ('long')"
+        
+        # Assert that the index isn't modified
+        assert_pandas_eland_frame_equal(pd_df, df1)
+
+    def test_es_if_exists_append_mapping_mismatch_no_schema_enforcement(self):
+        df1 = pandas_to_eland(
+            pd_df,
+            es_client=ES_TEST_CLIENT,
+            es_dest_index="test-index",
+            es_if_exists="append",
+            es_refresh=True,
         )
+
+        df2 = pandas_to_eland(
+            pd_df2,
+            es_client=ES_TEST_CLIENT,
+            es_dest_index="test-index",
+            es_if_exists="append",
+        )
+
+        pr
+
+        
         # Assert that the index isn't modified
         assert_pandas_eland_frame_equal(pd_df, df1)