diff --git a/src/include/utils/wait_event.h b/src/include/utils/wait_event.h
index 080e92d1cf..1b735d4a0e 100644
--- a/src/include/utils/wait_event.h
+++ b/src/include/utils/wait_event.h
@@ -53,12 +53,6 @@ extern PGDLLIMPORT uint32 *my_wait_event_info;
  *
  * The ID retrieved can be used with pgstat_report_wait_start() or equivalent.
  */
-typedef enum
-{
-	WAIT_EVENT_EXTENSION = PG_WAIT_EXTENSION,
-	WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED,
-} WaitEventExtension;
-
 extern void WaitEventExtensionShmemInit(void);
 extern Size WaitEventExtensionShmemSize(void);
 
diff --git a/src/backend/utils/activity/wait_event.c b/src/backend/utils/activity/wait_event.c
index 4ffcb10c8b..084a9dfdc2 100644
--- a/src/backend/utils/activity/wait_event.c
+++ b/src/backend/utils/activity/wait_event.c
@@ -89,8 +89,7 @@ typedef struct WaitEventExtensionCounterData
 static WaitEventExtensionCounterData *WaitEventExtensionCounter;
 
 /* first event ID of custom wait events for extensions */
-#define NUM_BUILTIN_WAIT_EVENT_EXTENSION	\
-	(WAIT_EVENT_EXTENSION_FIRST_USER_DEFINED - WAIT_EVENT_EXTENSION)
+#define WAIT_EVENT_EXTENSION_INITIAL_ID	1
 
 /* wait event info for extensions */
 #define WAIT_EVENT_EXTENSION_INFO(eventId)	(PG_WAIT_EXTENSION | eventId)
@@ -129,7 +128,7 @@ WaitEventExtensionShmemInit(void)
 	if (!found)
 	{
 		/* initialize the allocation counter and its spinlock. */
-		WaitEventExtensionCounter->nextId = NUM_BUILTIN_WAIT_EVENT_EXTENSION;
+		WaitEventExtensionCounter->nextId = WAIT_EVENT_EXTENSION_INITIAL_ID;
 		SpinLockInit(&WaitEventExtensionCounter->mutex);
 	}
 
@@ -244,7 +243,7 @@ GetWaitEventExtensionIdentifier(uint16 eventId)
 	WaitEventExtensionEntryById *entry;
 
 	/* Built-in event? */
-	if (eventId < NUM_BUILTIN_WAIT_EVENT_EXTENSION)
+	if (eventId < WAIT_EVENT_EXTENSION_INITIAL_ID)
 		return "Extension";
 
 	/* It is a user-defined wait event, so lookup hash table. */
diff --git a/contrib/pg_prewarm/autoprewarm.c b/contrib/pg_prewarm/autoprewarm.c
index 248b9914a3..1c8804dc43 100644
--- a/contrib/pg_prewarm/autoprewarm.c
+++ b/contrib/pg_prewarm/autoprewarm.c
@@ -226,7 +226,7 @@ autoprewarm_main(Datum main_arg)
 			(void) WaitLatch(MyLatch,
 							 WL_LATCH_SET | WL_EXIT_ON_PM_DEATH,
 							 -1L,
-							 WAIT_EVENT_EXTENSION);
+							 PG_WAIT_EXTENSION);
 		}
 		else
 		{
@@ -253,7 +253,7 @@ autoprewarm_main(Datum main_arg)
 			(void) WaitLatch(MyLatch,
 							 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
 							 delay_in_ms,
-							 WAIT_EVENT_EXTENSION);
+							 PG_WAIT_EXTENSION);
 		}
 
 		/* Reset the latch, loop. */