diff --git a/pyproject.toml b/pyproject.toml
index 978e98fb..7a2ff1d7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -2,7 +2,7 @@
 name = "stcal"
 description = "STScI tools and algorithms used in calibration pipelines"
 readme = "README.md"
-requires-python = ">=3.10"
+requires-python = ">=3.10,<3.13"
 authors = [
     { name = "STScI", email = "help@stsci.edu" },
 ]