diff --git a/tests/headers/enum_explicit_type.hpp b/tests/headers/enum_explicit_type.hpp
index 78eadd4032..b2a4307e5e 100644
--- a/tests/headers/enum_explicit_type.hpp
+++ b/tests/headers/enum_explicit_type.hpp
@@ -5,7 +5,7 @@ enum Foo: unsigned char {
     Qux
 };
 
-enum Neg: char {
+enum Neg: signed char {
     MinusOne = -1,
     One = 1,
 };