diff --git a/Makefile b/Makefile
index 20bdff1..f43919e 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,7 @@ ZENSICAL := uvx --with pyyaml==6.0.2 zensical@$(ZENSICAL_VERSION)
 # developed against. Pinned so a validator release cannot change what CI means without a
 # commit here. --meta . points it at THIS working tree rather than a released tag, so a
 # rule added in a branch is enforced by the run that introduces it.
-OOLD_VERSION ?= 1.0.1
+OOLD_VERSION ?= 2.0.0
 OOLD := uv run --with "oold[validation]==$(OOLD_VERSION)" oold
 
 .PHONY: validate