diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index 11fe9bf..6dfe446 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -34,9 +34,11 @@
 #else
 #include <stdio.h>
 #include <stdlib.h>
+#if defined(MBEDTLS_HAVE_TIME)
 #include <time.h>
 #define mbedtls_time            time
 #define mbedtls_time_t          time_t
+#endif
 #define mbedtls_printf          printf
 #define mbedtls_calloc          calloc
 #define mbedtls_free            free
@@ -823,6 +825,7 @@
 
     get_options( argc, argv );
 
+#if defined(MBEDTLS_HAVE_TIME)
     /*
      * Decisions to drop/delay/duplicate packets are pseudo-random: dropping
      * exactly 1 in N packets would lead to problems when a flight has exactly
@@ -833,11 +836,12 @@
      */
     if( opt.seed == 0 )
     {
-        opt.seed = (unsigned int) time( NULL );
+        opt.seed = (unsigned int) mbedtls_time( NULL );
         mbedtls_printf( "  . Pseudo-random seed: %u\n", opt.seed );
     }
 
     srand( opt.seed );
+#endif /* MBEDTLS_HAVE_TIME */
 
     /*
      * 0. "Connect" to the server