diff --git a/tools/pyproject.toml b/tools/pyproject.toml
index ba0938e..a32bb48 100644
--- a/tools/pyproject.toml
+++ b/tools/pyproject.toml
@@ -26,7 +26,7 @@ dependencies = [
     # identifiers no longer resolve to falsy defaults), which breaks the invariant
     # linter's evaluability contract (see tests/unit/validation/linters/test_invariants*).
     # Do not relax this cap without updating that evaluation logic and its tests.
-    "cel-python>=0.4.0,<0.5.0",
+    "cel-python>=0.4.0,<0.6.0",
 ]
 
 [project.optional-dependencies]