diff --git a/tools/BUILD b/tools/BUILD
index c51e8747e..b8a621f84 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -31,7 +31,7 @@ java_package_configuration(
         "-Xep:CannotMockFinalClass:WARN",
         "-Xep:ClassCanBeStatic:WARN",
         "-Xep:ClassNewInstance:WARN",
-        "-Xep:DefaultCharset:WARN",
+        "-Xep:DefaultCharset:ERROR",
         "-Xep:DoubleCheckedLocking:WARN",
         "-Xep:ElementsCountedInLoop:WARN",
         "-Xep:EqualsHashCode:WARN",