diff --git a/testsuite/testutils.c b/testsuite/testutils.c
index 1b3e23c0e14b203ec9bfc583a5bbd4f77207cc10..418faa1293f5a623c42f8b4e054d84cd17fa9a58 100644
--- a/testsuite/testutils.c
+++ b/testsuite/testutils.c
@@ -109,7 +109,7 @@ decode_hex_dup(const char *hex)
 }
 
 void
-print_hex(unsigned length, uint8_t *data)
+print_hex(unsigned length, const uint8_t *data)
 {
   unsigned i;
   
diff --git a/testsuite/testutils.h b/testsuite/testutils.h
index ae2f8b79ace1554a40b4a39a74e1bfde26f05566..2eb02a655a0b9645165334334b88427af697c8e3 100644
--- a/testsuite/testutils.h
+++ b/testsuite/testutils.h
@@ -35,7 +35,7 @@ const uint8_t *
 decode_hex_dup(const char *hex);
 
 void
-print_hex(unsigned length, uint8_t *data);
+print_hex(unsigned length, const uint8_t *data);
 
 /* The main program */
 int