diff --git a/tests/suites/test_suite_x509write.function b/tests/suites/test_suite_x509write.function
index 8b57f8c..ca097e7 100644
--- a/tests/suites/test_suite_x509write.function
+++ b/tests/suites/test_suite_x509write.function
@@ -21,7 +21,7 @@
     int ret;
     size_t olen = 0, pem_len = 0;
     FILE *f;
-    char *subject_name = "C=NL,O=PolarSSL,CN=PolarSSL Server 1";
+    const char *subject_name = "C=NL,O=PolarSSL,CN=PolarSSL Server 1";
     rnd_pseudo_info rnd_info;
 
     memset( &rnd_info, 0x2a, sizeof( rnd_pseudo_info ) );