diff --git a/programs/test/metatest.c b/programs/test/metatest.c
index 9d90d8c..d876e9a 100644
--- a/programs/test/metatest.c
+++ b/programs/test/metatest.c
@@ -128,7 +128,7 @@
     volatile char *volatile p;
     set_to_zero_but_the_compiler_does_not_know(&p, sizeof(p));
     /* Undefined behavior (read from null data pointer) */
-    mbedtls_printf("%p -> %u\n", p, (unsigned) *p);
+    mbedtls_printf("%p -> %u\n", (void *) p, (unsigned) *p);
 }
 
 static void null_pointer_call(const char *name)