diff --git a/tools/BUILD b/tools/BUILD
index 6d15a21..19db90b 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -44,7 +44,7 @@
         "-Xep:FunctionalInterfaceClash:ERROR",
         "-Xep:FutureReturnValueIgnored:ERROR",
         "-Xep:GetClassOnEnum:ERROR",
-        "-Xep:ImmutableAnnotationChecker:WARN",
+        "-Xep:ImmutableAnnotationChecker:ERROR",
         "-Xep:ImmutableEnumChecker:WARN",
         "-Xep:IncompatibleModifiers:ERROR",
         "-Xep:InjectOnConstructorOfAbstractClass:ERROR",