diff --git a/setup.py b/setup.py
index 18857da2..a00e4a01 100755
--- a/setup.py
+++ b/setup.py
@@ -92,7 +92,8 @@ def read(*parts):
     # >=3.7 for dataclass, capture_output, dict ordering, np>=1.20.
     # ==3.7 for Colab
     # ==3.9 for the DAPPER/GCP cluster, since dill isn't compat. across versions.
-    python_requires='>=3.9',
+    # <3.11 because it failed with multiprocessing
+    python_requires='>=3.9,<3.11',
     install_requires=INSTALL_REQUIRES,
     extras_require=EXTRAS,