diff --git a/setup.py b/setup.py
index 706feb9..c557709 100644
--- a/setup.py
+++ b/setup.py
@@ -21,5 +21,5 @@
     url="https://pyett.readthedocs.io/",
     license=license,
     packages=find_packages(exclude=["contrib", "docs", "tests"]),
-    install_requires=["requests==2.22.0", "pandas==1.0.3", "nbsphinx==0.8.6", "aiohttp==3.6.2"],
+    install_requires=["requests==2.22.0", "pandas==1.0.3", "nbsphinx==0.8.6", "aiohttp==3.6.2", "lxml"],
 )