diff --git a/common_smp/inc/tx_api.h b/common_smp/inc/tx_api.h
index ae5ffc8f..cc378f16 100644
--- a/common_smp/inc/tx_api.h
+++ b/common_smp/inc/tx_api.h
@@ -334,6 +334,14 @@ extern   "C" {
 #endif
 
 
+/* Define the default maximum message size in a queue. The default value is TX_16_ULONG, but may
+   be customized in tx_user.h or as a compilation option. */
+
+#ifndef TX_QUEUE_MESSAGE_MAX_SIZE
+#define TX_QUEUE_MESSAGE_MAX_SIZE           TX_16_ULONG
+#endif
+
+
 /* Event numbers 0 through 4095 are reserved by Azure RTOS. Specific event assignments are:
 
                                 ThreadX events:     1-199