diff --git a/pyproject.toml b/pyproject.toml
index 438e34d..b3749d7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -33,8 +33,13 @@ dependencies = [
     # branch), breaking calibrate(); cap until oguk migrates to the
     # income-heterogeneity API.
     "ogcore>=0.15.6,<0.18",
-    "policyengine>=4.22",
-    "policyengine-uk>=2.89.2",
+    # Depend on the umbrella package's uk extra rather than flooring
+    # policyengine-uk separately: `uk_latest` reports the version from
+    # policyengine's bundled manifest, not the installed package, so an
+    # independent floor cannot raise the model version actually simulated
+    # against -- it only decouples the two and downgrades the mismatch to
+    # a UserWarning. The extra keeps them in lockstep.
+    "policyengine[uk]>=5.0,<6",
     "requests>=2.31",
     "rich>=13.0",
     "openpyxl>=3.1",