diff --git a/lib/libmd/tests/Makefile b/lib/libmd/tests/Makefile
--- a/lib/libmd/tests/Makefile
+++ b/lib/libmd/tests/Makefile
@@ -2,9 +2,6 @@
 
 PACKAGE=	tests
 
-# XXX
-WARNS=	0
-
 ATF_TESTS_SH=	libmd_test
 
 MDTESTS=	md rmd sha skein
diff --git a/lib/libmd/tests/mddriver.c b/lib/libmd/tests/mddriver.c
--- a/lib/libmd/tests/mddriver.c
+++ b/lib/libmd/tests/mddriver.c
@@ -37,8 +37,8 @@
 #endif
 
 /* Digests a string and prints the result. */
-static void 
-MDString(char *string)
+static void
+MDString(const char *string)
 {
 	char buf[33];
 
diff --git a/lib/libmd/tests/rmddriver.c b/lib/libmd/tests/rmddriver.c
--- a/lib/libmd/tests/rmddriver.c
+++ b/lib/libmd/tests/rmddriver.c
@@ -20,8 +20,8 @@
 #include "ripemd.h"
 
 /* Digests a string and prints the result. */
-static void 
-RIPEMD160String(char *string)
+static void
+RIPEMD160String(const char *string)
 {
 	char buf[2*20 + 1];
 
diff --git a/lib/libmd/tests/shadriver.c b/lib/libmd/tests/shadriver.c
--- a/lib/libmd/tests/shadriver.c
+++ b/lib/libmd/tests/shadriver.c
@@ -58,7 +58,7 @@
 
 /* Digests a string and prints the result. */
 static void
-SHAString(char *string)
+SHAString(const char *string)
 {
 	char buf[2*64 + 1];
 
diff --git a/lib/libmd/tests/skeindriver.c b/lib/libmd/tests/skeindriver.c
--- a/lib/libmd/tests/skeindriver.c
+++ b/lib/libmd/tests/skeindriver.c
@@ -41,7 +41,7 @@
 
 /* Digests a string and prints the result. */
 static void
-SKEINString(char *string)
+SKEINString(const char *string)
 {
 	char buf[2*128 + 1];