diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 41973b7..b2d5574 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -501,6 +501,7 @@
    MBEDTLS_SSL_TLS_PRF_SHA256
 }
 mbedtls_tls_prf_types;
+
 /**
  * \brief          Callback type: send data on the network.
  *
@@ -626,6 +627,11 @@
 typedef struct mbedtls_ssl_flight_item mbedtls_ssl_flight_item;
 #endif
 
+/* TODO: Document */
+typedef int mbedtls_ssl_cache_get_t( void *data, mbedtls_ssl_session *session );
+/* TODO: Document */
+typedef int mbedtls_ssl_cache_set_t( void *data, const mbedtls_ssl_session *session );
+
 #if defined(MBEDTLS_SSL_ASYNC_PRIVATE)
 #if defined(MBEDTLS_X509_CRT_PARSE_C)
 /**
@@ -968,9 +974,9 @@
     void *p_rng;                    /*!< context for the RNG function       */
 
     /** Callback to retrieve a session from the cache                       */
-    int (*f_get_cache)(void *, mbedtls_ssl_session *);
+    mbedtls_ssl_cache_get_t *f_get_cache;
     /** Callback to store a session into the cache                          */
-    int (*f_set_cache)(void *, const mbedtls_ssl_session *);
+    mbedtls_ssl_cache_set_t *f_set_cache;
     void *p_cache;                  /*!< context for cache callbacks        */
 
 #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
@@ -2428,9 +2434,9 @@
  * \param f_set_cache    session set callback
  */
 void mbedtls_ssl_conf_session_cache( mbedtls_ssl_config *conf,
-        void *p_cache,
-        int (*f_get_cache)(void *, mbedtls_ssl_session *),
-        int (*f_set_cache)(void *, const mbedtls_ssl_session *) );
+                                     void *p_cache,
+                                     mbedtls_ssl_cache_get_t *f_get_cache,
+                                     mbedtls_ssl_cache_set_t *f_set_cache );
 #endif /* MBEDTLS_SSL_SRV_C */
 
 #if defined(MBEDTLS_SSL_CLI_C)