diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 84c78c4..650dec7 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -8217,8 +8217,14 @@
                   void (*f_dbg)(void *, int, const char *, int, const char *),
                   void  *p_dbg )
 {
+#if defined(MBEDTLS_DEBUG_C)
     conf->f_dbg      = f_dbg;
     conf->p_dbg      = p_dbg;
+#else
+    ((void) conf);
+    ((void) f_dbg);
+    ((void) p_dbg);
+#endif /* MBEDTLS_DEBUG_C */
 }
 
 #if !defined(MBEDTLS_SSL_CONF_RECV) && \