diff --git a/programs/x509/cert_app.c b/programs/x509/cert_app.c
index 84f67e6..2ebb77c 100644
--- a/programs/x509/cert_app.c
+++ b/programs/x509/cert_app.c
@@ -54,6 +54,7 @@
 #include "mbedtls/net.h"
 #include "mbedtls/ssl.h"
 #include "mbedtls/x509.h"
+#include "mbedtls/debug.h"
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -377,6 +378,10 @@
 
         mbedtls_printf( " ok\n" );
 
+#if defined(MBEDTLS_DEBUG_C)
+        mbedtls_debug_set_threshold( opt.debug_level );
+#endif
+
         /*
          * 2. Start the connection
          */