diff --git a/ChangeLog.d/tls13-custom-config.txt b/ChangeLog.d/tls13-custom-config.txt
new file mode 100644
index 000000000..da2e25d95
--- /dev/null
+++ b/ChangeLog.d/tls13-custom-config.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix undefined symbols in some builds using TLS 1.3 with a custom
+     configuration file.
diff --git a/include/mbedtls/mbedtls_config.h b/include/mbedtls/mbedtls_config.h
index f34c0913f..df53041f0 100644
--- a/include/mbedtls/mbedtls_config.h
+++ b/include/mbedtls/mbedtls_config.h
@@ -4055,7 +4055,7 @@
  * This is not used in TLS 1.2.
  *
  */
-#define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000
+//#define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000
 
 /**
  * \def MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH
@@ -4064,7 +4064,7 @@
  *
  * This must be less than 256.
  */
-#define MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH 32
+//#define MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH 32
 
 /**
  * \def MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS
@@ -4074,7 +4074,7 @@
  * the MBEDTLS_SSL_SESSION_TICKETS option is enabled.
  *
  */
-#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1
+//#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1
 
 /* X509 options */
 //#define MBEDTLS_X509_MAX_INTERMEDIATE_CA   8   /**< Maximum number of intermediate CAs in a verification chain. */
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 920efa98c..a3ecbfbf6 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -405,6 +405,18 @@
 #define MBEDTLS_SSL_CID_TLS1_3_PADDING_GRANULARITY 16
 #endif
 
+#if !defined(MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE)
+#define MBEDTLS_SSL_TLS1_3_TICKET_AGE_TOLERANCE 6000
+#endif
+
+#if !defined(MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH)
+#define MBEDTLS_SSL_TLS1_3_TICKET_NONCE_LENGTH 32
+#endif
+
+#if !defined(MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS)
+#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1
+#endif
+
 /** \} name SECTION: Module settings */
 
 /*