diff --git a/taxoniumtools/setup.cfg b/taxoniumtools/setup.cfg
index a39ee922..e28e0e2a 100644
--- a/taxoniumtools/setup.cfg
+++ b/taxoniumtools/setup.cfg
@@ -22,7 +22,7 @@ python_requires = >=3.8
 install_requires =
     treeswift
     alive-progress
-    biopython
+    biopython<=1.81
     pandas
     google-api-python-client
     protobuf<4