diff --git a/include/mbedtls/des.h b/include/mbedtls/des.h
index 6eb7d03..50c69bc 100644
--- a/include/mbedtls/des.h
+++ b/include/mbedtls/des.h
@@ -336,6 +336,8 @@
 void mbedtls_des_setkey( uint32_t SK[32],
                          const unsigned char key[MBEDTLS_DES_KEY_SIZE] );
 
+#if defined(MBEDTLS_SELF_TEST)
+
 /**
  * \brief          Checkup routine
  *
@@ -343,6 +345,8 @@
  */
 int mbedtls_des_self_test( int verbose );
 
+#endif /* MBEDTLS_SELF_TEST */
+
 #ifdef __cplusplus
 }
 #endif