diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 84c83e3..36ca0d6 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2397,7 +2397,7 @@
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
         return( ret );
     }
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write hello verify request" ) );
 
@@ -3385,7 +3385,7 @@
         MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_flight_transmit", ret );
         return( ret );
     }
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write server hello done" ) );
 
@@ -4264,7 +4264,7 @@
         if( ( ret = mbedtls_ssl_flight_transmit( ssl ) ) != 0 )
             return( ret );
     }
-#endif
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
 
     switch( ssl->state )
     {