diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 29d9906..496f7e1 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -683,6 +683,13 @@
 #define "MBEDTLS_SSL_CONF_SEND/RECV/RECV_TIMEOUT must be defined simultaneously"
 #endif
 
+#if ( defined(MBEDTLS_SSL_CONF_GET_TIMER) &&            \
+      !defined(MBEDTLS_SSL_CONF_SET_TIMER) ) || \
+    ( !defined(MBEDTLS_SSL_CONF_GET_TIMER) &&           \
+      defined(MBEDTLS_SSL_CONF_SET_TIMER) )
+#define "MBEDTLS_SSL_CONF_GET_TIMER and MBEDTLS_SSL_CONF_SET_TIMER must be defined together."
+#endif
+
 #if defined(MBEDTLS_SSL_TICKET_C) && !defined(MBEDTLS_CIPHER_C)
 #error "MBEDTLS_SSL_TICKET_C defined, but not all prerequisites"
 #endif
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index a767cb2..da1ae42 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -3601,6 +3601,18 @@
 //#define MBEDTLS_SSL_CONF_CID_LEN 0
 //#define MBEDTLS_SSL_CONF_IGNORE_UNEXPECTED_CID MBEDTLS_SSL_UNEXPECTED_CID_IGNORE
 
+/* The timer callbacks to use by the SSL module.
+ * If defined,
+ * - MBEDTLS_SSL_CONF_SET_TIMER must evaluate to the name of an externally
+ *   defined function with signature
+ *      void (*f_set_timer)( void* , uint32_t, uint32_t ),
+ * * MBEDTLS_SSL_CONF_SEND must evaluate to the name of an externally
+ *   defined function with signature
+ *      int (*f_get_timer)( void* ).
+ */
+//#define MBEDTLS_SSL_CONF_GET_TIMER mbedtls_timing_get_delay
+//#define MBEDTLS_SSL_CONF_SET_TIMER mbedtls_timing_set_delay
+
 /* The send and receive callbacks to use by the SSL module.
  * If defined,
  * - MBEDTLS_SSL_CONF_RECV must evaluate to the name of an externally
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 671d107..f422d44 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -1183,8 +1183,12 @@
      */
     void *p_timer;              /*!< context for the timer callbacks */
 
+#if !defined(MBEDTLS_SSL_CONF_SET_TIMER)
     mbedtls_ssl_set_timer_t *f_set_timer;       /*!< set timer callback */
+#endif /* !MBEDTLS_SSL_CONF_SET_TIMER */
+#if !defined(MBEDTLS_SSL_CONF_GET_TIMER)
     mbedtls_ssl_get_timer_t *f_get_timer;       /*!< get timer callback */
+#endif /* !MBEDTLS_SSL_CONF_GET_TIMER */
 
     /*
      * Record layer (incoming data)
@@ -1779,6 +1783,8 @@
 void mbedtls_ssl_conf_read_timeout( mbedtls_ssl_config *conf, uint32_t timeout );
 #endif /* !MBEDTLS_SSL_CONF_READ_TIMEOUT */
 
+#if !defined(MBEDTLS_SSL_CONF_SET_TIMER) && \
+    !defined(MBEDTLS_SSL_CONF_GET_TIMER)
 /**
  * \brief          Set the timer callbacks (Mandatory for DTLS.)
  *
@@ -1796,6 +1802,12 @@
  *                 \c mbedtls_timing_get_delay() that are suitable for using
  *                 here, except if using an event-driven style.
  *
+ * \note           On constrained systems, the timer callbacks \p f_set_timer
+ *                 and \p f_get_timer may also be configured at compile-time
+ *                 via MBEDTLS_SSL_CONF_GET_TIMER and MBEDTLS_SSL_CONF_SET_TIMER.
+ *                 In this case, the corresponding arguments to this function
+ *                 are ignored.
+ *
  * \note           See also the "DTLS tutorial" article in our knowledge base.
  *                 https://tls.mbed.org/kb/how-to/dtls-tutorial
  */
@@ -1803,6 +1815,18 @@
                                void *p_timer,
                                mbedtls_ssl_set_timer_t *f_set_timer,
                                mbedtls_ssl_get_timer_t *f_get_timer );
+#else
+/**
+ * \brief          Set the context to be passed to the timer callbacks
+ *                 (Mandatory for DTLS.)
+ *
+ * \param ssl      The SSL context to configure.
+ * \param p_timer  The context to be passed to the timer callbacks.
+ *
+ */
+void mbedtls_ssl_set_timer_cb_ctx( mbedtls_ssl_context *ssl,
+                                   void *p_timer );
+#endif
 
 /**
  * \brief           Callback type: generate and write session ticket
diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 8d5170c..4b85781 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1291,6 +1291,44 @@
 
 typedef int (*mbedtls_frng_t)( void*, unsigned char*, size_t );
 
+#if !defined(MBEDTLS_SSL_CONF_SET_TIMER)
+static inline mbedtls_ssl_set_timer_t* mbedtls_ssl_get_set_timer(
+    mbedtls_ssl_context const *ssl )
+{
+    return( ssl->f_set_timer );
+}
+#else /* !MBEDTLS_SSL_CONF_SET_TIMER */
+
+#define mbedtls_ssl_conf_set_timer_func MBEDTLS_SSL_CONF_SET_TIMER
+extern void mbedtls_ssl_conf_set_timer_func( void*, uint32_t, uint32_t );
+
+static inline mbedtls_ssl_set_timer_t* mbedtls_ssl_get_set_timer(
+    mbedtls_ssl_context const *ssl )
+{
+    ((void) ssl);
+    return ((mbedtls_ssl_set_timer_t*) mbedtls_ssl_conf_set_timer_func);
+}
+#endif /* MBEDTLS_SSL_CONF_SET_TIMER */
+
+#if !defined(MBEDTLS_SSL_CONF_GET_TIMER)
+static inline mbedtls_ssl_get_timer_t* mbedtls_ssl_get_get_timer(
+    mbedtls_ssl_context const *ssl )
+{
+    return( ssl->f_get_timer );
+}
+#else /* !MBEDTLS_SSL_CONF_GET_TIMER */
+
+#define mbedtls_ssl_conf_get_timer_func MBEDTLS_SSL_CONF_GET_TIMER
+extern int mbedtls_ssl_conf_get_timer_func( void* );
+
+static inline mbedtls_ssl_get_timer_t* mbedtls_ssl_get_get_timer(
+    mbedtls_ssl_context const *ssl )
+{
+    ((void) ssl);
+    return ((mbedtls_ssl_get_timer_t*) mbedtls_ssl_conf_get_timer_func);
+}
+#endif /* MBEDTLS_SSL_CONF_GET_TIMER */
+
 #if !defined(MBEDTLS_SSL_CONF_RECV)
 static inline mbedtls_ssl_recv_t* mbedtls_ssl_get_recv(
     mbedtls_ssl_context const *ssl )