diff --git a/library/ssl_cli.c b/library/ssl_cli.c
index 772b2c9..a80a769 100644
--- a/library/ssl_cli.c
+++ b/library/ssl_cli.c
@@ -302,6 +302,7 @@
 }
 #endif /* POLARSSL_SSL_MAX_FRAGMENT_LENGTH */
 
+#if defined(POLARSSL_SSL_TRUNCATED_HMAC)
 static void ssl_write_truncated_hmac_ext( ssl_context *ssl,
                                           unsigned char *buf, size_t *olen )
 {
@@ -323,6 +324,7 @@
 
     *olen = 4;
 }
+#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
 
 #if defined(POLARSSL_SSL_SESSION_TICKETS)
 static void ssl_write_session_ticket_ext( ssl_context *ssl,
@@ -553,8 +555,10 @@
     ext_len += olen;
 #endif
 
+#if defined(POLARSSL_SSL_TRUNCATED_HMAC)
     ssl_write_truncated_hmac_ext( ssl, p + 2 + ext_len, &olen );
     ext_len += olen;
+#endif
 
 #if defined(POLARSSL_SSL_SESSION_TICKETS)
     ssl_write_session_ticket_ext( ssl, p + 2 + ext_len, &olen );
@@ -645,6 +649,7 @@
 }
 #endif /* POLARSSL_SSL_MAX_FRAGMENT_LENGTH */
 
+#if defined(POLARSSL_SSL_TRUNCATED_HMAC)
 static int ssl_parse_truncated_hmac_ext( ssl_context *ssl,
                                          const unsigned char *buf,
                                          size_t len )
@@ -661,6 +666,7 @@
 
     return( 0 );
 }
+#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
 
 #if defined(POLARSSL_SSL_SESSION_TICKETS)
 static int ssl_parse_session_ticket_ext( ssl_context *ssl,
@@ -910,6 +916,7 @@
             break;
 #endif /* POLARSSL_SSL_MAX_FRAGMENT_LENGTH */
 
+#if defined(POLARSSL_SSL_TRUNCATED_HMAC)
         case TLS_EXT_TRUNCATED_HMAC:
             SSL_DEBUG_MSG( 3, ( "found truncated_hmac extension" ) );
 
@@ -920,6 +927,7 @@
             }
 
             break;
+#endif /* POLARSSL_SSL_TRUNCATED_HMAC */
 
 #if defined(POLARSSL_SSL_SESSION_TICKETS)
         case TLS_EXT_SESSION_TICKET: