diff --git a/tests/utiltest.c b/tests/utiltest.c
index 3a1f8ebbe9b259f7a9096740f3f8d7ba41abef1e..98c689d07c74de53dea8a6d6be7c39e4a64ced7c 100644
--- a/tests/utiltest.c
+++ b/tests/utiltest.c
@@ -184,8 +184,8 @@ static int
 testOverflowCheckMacro(const void *data ATTRIBUTE_UNUSED)
 {
     long long tmp;
-    unsigned char luchar;
-    char lchar;
+    uint8_t luchar;
+    int8_t lchar;
 
     TEST_OVERFLOW(luchar, 254, false);
     TEST_OVERFLOW(luchar, 255, false);