diff --git a/tests/unittests/tests-hashes/tests-hashes-sha512.c b/tests/unittests/tests-hashes/tests-hashes-sha512.c
index 122fa1b564..f4535eb849 100644
--- a/tests/unittests/tests-hashes/tests-hashes-sha512.c
+++ b/tests/unittests/tests-hashes/tests-hashes-sha512.c
@@ -341,7 +341,7 @@ static void test_hashes_sha512_hash_sequence_binary(void)
 
 static void test_hashes_sha512_hash_update_twice(void)
 {
-    static const char *teststring = "abcdef";
+    static const char teststring[] = "abcdef";
 
     static uint8_t hash_update_once[SHA512_DIGEST_LENGTH];
     static uint8_t hash_update_twice[SHA512_DIGEST_LENGTH];