diff --git a/action.yml b/action.yml
index fd37fc7..82ae815 100644
--- a/action.yml
+++ b/action.yml
@@ -57,7 +57,11 @@ runs:
           # into every consumer's CI with no commit here to review it. The
           # `latest-patchrail` job in .github/workflows/test.yml runs this same
           # path against the newest release, so the range moves deliberately.
-          python -m pip install --quiet "patchrail>=0.3.1,<0.5.0"
+          #
+          # Floor is 0.5.0: every release below it reads a tool the job merely
+          # named — a `GRADLE_HOME=` line, a `Collecting mypy` from pip — as the
+          # cause of death, so it annotates the PR with a confident wrong answer.
+          python -m pip install --quiet "patchrail>=0.5.0,<0.6.0"
         fi
 
     - name: Explain failure and annotate
diff --git a/tests/test_schema_guard.py b/tests/test_schema_guard.py
index 2dfe134..5fcd607 100644
--- a/tests/test_schema_guard.py
+++ b/tests/test_schema_guard.py
@@ -26,7 +26,7 @@
 # test agree with any future edit to it, which is the drift it exists to catch.
 SUPPORTED_SCHEMA = "patchrail.ci_result.v1"
 
-# What patchrail emits today (verified against 0.3.1 and 0.4.0).
+# What patchrail emits today (verified against 0.3.1, 0.4.0 and 0.5.0).
 V1_RESULT = {
     "schema_version": SUPPORTED_SCHEMA,
     "failure_class": "python_test_failure",