diff --git a/library/ssl_tls13_keys.h b/library/ssl_tls13_keys.h
index 64caa8a..ee6572f 100644
--- a/library/ssl_tls13_keys.h
+++ b/library/ssl_tls13_keys.h
@@ -21,30 +21,30 @@
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
 
-/* This requires MBEDTLS_SSL_TLS1_3_LABEL( name, string ) to be defined at
+/* This requires MBEDTLS_SSL_TLS1_3_LABEL( idx, name, string ) to be defined at
  * the point of use. See e.g. the definition of mbedtls_ssl_tls1_3_labels_union
  * below. */
 #define MBEDTLS_SSL_TLS1_3_LABEL_LIST                               \
-    MBEDTLS_SSL_TLS1_3_LABEL( finished    , "finished"     )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( resumption  , "resumption"   )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( traffic_upd , "traffic upd"  )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( exporter    , "exporter"     )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( key         , "key"          )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( iv          , "iv"           )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( sn          , "sn"           )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( c_hs_traffic, "c hs traffic" )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( c_ap_traffic, "c ap traffic" )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( c_e_traffic , "c e traffic"  )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( s_hs_traffic, "s hs traffic" )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( s_ap_traffic, "s ap traffic" )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( s_e_traffic , "s e traffic"  )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( exp_master  , "exp master"   )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( res_master  , "res master"   )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( ext_binder  , "ext binder"   )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( res_binder  , "res binder"   )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( derived     , "derived"      )
+    MBEDTLS_SSL_TLS1_3_LABEL( 0,  finished    , "finished"     ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 1,  resumption  , "resumption"   ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 2,  traffic_upd , "traffic upd"  ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 3,  exporter    , "exporter"     ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 4,  key         , "key"          ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 5,  iv          , "iv"           ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 6,  sn          , "sn"           ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 7,  c_hs_traffic, "c hs traffic" ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 8,  c_ap_traffic, "c ap traffic" ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 9,  c_e_traffic , "c e traffic"  ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 10, s_hs_traffic, "s hs traffic" ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 11, s_ap_traffic, "s ap traffic" ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 12, s_e_traffic , "s e traffic"  ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 13, exp_master  , "exp master"   ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 14, res_master  , "res master"   ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 15, ext_binder  , "ext binder"   ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 16, res_binder  , "res binder"   ) \
+    MBEDTLS_SSL_TLS1_3_LABEL( 17, derived     , "derived"      )
 
-#define MBEDTLS_SSL_TLS1_3_LABEL( name, string ) \
+#define MBEDTLS_SSL_TLS1_3_LABEL( idx, name, string )       \
     const unsigned char name    [ sizeof(string) - 1 ];
 
 union mbedtls_ssl_tls1_3_labels_union