diff --git a/library/ssl_tls13_keys.h b/library/ssl_tls13_keys.h
index a35e085..9efeb04 100644
--- a/library/ssl_tls13_keys.h
+++ b/library/ssl_tls13_keys.h
@@ -20,25 +20,31 @@
 #define MBEDTLS_SSL_TLS1_3_KEYS_H
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
-#define MBEDTLS_SSL_TLS1_3_LABEL_LIST                                   \
-    const unsigned char finished    [ sizeof("finished")     - 1 ];     \
-    const unsigned char resumption  [ sizeof("resumption")   - 1 ];     \
-    const unsigned char traffic_upd [ sizeof("traffic upd")  - 1 ];     \
-    const unsigned char export      [ sizeof("exporter")     - 1 ];     \
-    const unsigned char key         [ sizeof("key")          - 1 ];     \
-    const unsigned char iv          [ sizeof("iv")           - 1 ];     \
-    const unsigned char sn          [ sizeof("sn")           - 1 ];     \
-    const unsigned char c_hs_traffic[ sizeof("c hs traffic") - 1 ];     \
-    const unsigned char c_ap_traffic[ sizeof("c ap traffic") - 1 ];     \
-    const unsigned char c_e_traffic [ sizeof("c e traffic")  - 1 ];     \
-    const unsigned char s_hs_traffic[ sizeof("s hs traffic") - 1 ];     \
-    const unsigned char s_ap_traffic[ sizeof("s ap traffic") - 1 ];     \
-    const unsigned char s_e_traffic [ sizeof("s e traffic")  - 1 ];     \
-    const unsigned char exp_master  [ sizeof("exp master")   - 1 ];     \
-    const unsigned char res_master  [ sizeof("res master")   - 1 ];     \
-    const unsigned char ext_binder  [ sizeof("ext binder")   - 1 ];     \
-    const unsigned char res_binder  [ sizeof("res binder")   - 1 ];     \
-    const unsigned char derived     [ sizeof("derived")      - 1 ];     \
+
+/* This requires LABEL( 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                               \
+    LABEL( finished    , "finished"     )                           \
+    LABEL( resumption  , "resumption"   )                           \
+    LABEL( traffic_upd , "traffic upd"  )                           \
+    LABEL( export      , "exporter"     )                           \
+    LABEL( key         , "key"          )                           \
+    LABEL( iv          , "iv"           )                           \
+    LABEL( sn          , "sn"           )                           \
+    LABEL( c_hs_traffic, "c hs traffic" )                           \
+    LABEL( c_ap_traffic, "c ap traffic" )                           \
+    LABEL( c_e_traffic , "c e traffic"  )                           \
+    LABEL( s_hs_traffic, "s hs traffic" )                           \
+    LABEL( s_ap_traffic, "s ap traffic" )                           \
+    LABEL( s_e_traffic , "s e traffic"  )                           \
+    LABEL( exp_master  , "exp master"   )                           \
+    LABEL( res_master  , "res master"   )                           \
+    LABEL( ext_binder  , "ext binder"   )                           \
+    LABEL( res_binder  , "res binder"   )                           \
+    LABEL( derived     , "derived"      )
+
+#define LABEL( name, string ) \
+    const unsigned char name    [ sizeof(string) - 1 ];
 
 union mbedtls_ssl_tls1_3_labels_union
 {
@@ -48,6 +54,8 @@
 {
     MBEDTLS_SSL_TLS1_3_LABEL_LIST
 };
+#undef LABEL
+
 extern const struct mbedtls_ssl_tls1_3_labels_struct mbedtls_ssl_tls1_3_labels;
 
 #define MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( LABEL )  \