diff --git a/lib/des/rctest.c b/lib/des/rctest.c
index 5b301b9a8..7d433d954 100644
--- a/lib/des/rctest.c
+++ b/lib/des/rctest.c
@@ -100,7 +100,7 @@ static unsigned char key3[16] =
     { 0x29, 0x04, 0x19, 0x72, 0xfb, 0x42, 0xba, 0x5f,
       0xc7, 0x12, 0x77, 0x12, 0xf1, 0x38, 0x29, 0xc9 };
 
-const char cipher3[] = 
+const unsigned char cipher3[] = 
     { 0x35, 0x81, 0x86, 0x99, 0x90, 0x01, 0xe6, 0xb5,
       0xda, 0xf0, 0x5e, 0xce, 0xeb, 0x7e, 0xee, 0x21,
       0xe0, 0x68, 0x9c, 0x1f, 0x00, 0xee, 0xa8, 0x1f,