diff --git a/os/rt/include/chregistry.h b/os/rt/include/chregistry.h
index 37cbde73f..47d675250 100644
--- a/os/rt/include/chregistry.h
+++ b/os/rt/include/chregistry.h
@@ -68,7 +68,8 @@ typedef struct {
   uint8_t   off_refs;               /**< @brief Offset of @p refs field.    */
   uint8_t   off_preempt;            /**< @brief Offset of @p ticks field.   */
   uint8_t   off_time;               /**< @brief Offset of @p time field.    */
-  uint8_t   off_reserved[5];
+  uint8_t   off_reserved[4];
+  uint8_t   intctxsize;             /**< @brief Size of a @p port_intctx.   */
   uint8_t   intervalsize;           /**< @brief Size of a @p sysinterval_t. */
   uint8_t   instancesnum;           /**< @brief Number of instances.        */
   uint8_t   off_sys_state;          /**< @brief Offset of @p state field.   */
diff --git a/os/rt/src/chregistry.c b/os/rt/src/chregistry.c
index 66183d72b..0be6ec015 100644
--- a/os/rt/src/chregistry.c
+++ b/os/rt/src/chregistry.c
@@ -85,6 +85,7 @@ ROMCONST chdebug_t ch_debug = {
   .timesize                 = (uint8_t)sizeof (systime_t),
   .intervalsize             = (uint8_t)sizeof (sysinterval_t),
   .threadsize               = (uint8_t)sizeof (thread_t),
+  .intctxsize               = (uint8_t)sizeof (struct port_intctx),
   .off_prio                 = (uint8_t)__CH_OFFSETOF(thread_t, hdr.pqueue.prio),
   .off_ctx                  = (uint8_t)__CH_OFFSETOF(thread_t, ctx),
   .off_newer                = (uint8_t)__CH_OFFSETOF(thread_t, rqueue.next),
@@ -112,7 +113,7 @@ ROMCONST chdebug_t ch_debug = {
 #else
   .off_time                 = (uint8_t)0,
 #endif
-  .off_reserved             = {(uint8_t)0, (uint8_t)0, (uint8_t)0, (uint8_t)0, (uint8_t)0},
+  .off_reserved             = {(uint8_t)0, (uint8_t)0, (uint8_t)0, (uint8_t)0},
   .instancesnum             = (uint8_t)PORT_CORES_NUMBER,
   .off_sys_state            = (uint8_t)__CH_OFFSETOF(ch_system_t, state),
   .off_sys_instances        = (uint8_t)__CH_OFFSETOF(ch_system_t, instances[0]),