diff --git a/pyproject.toml b/pyproject.toml
index 668826f5..17b14431 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,6 +37,7 @@ classifiers = [
 dependencies = [
   "coffea[dask] @ git+https://github.com/iasonkrom/coffea.git@preprocessing_backup",
   "dask-awkward>=2023.7.1,!=2023.8.0,<2023.9.1",
+  "matplotlib<3.8.0",
   "jupyterlab",
   "notebook",
   "nbclassic",