diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c
index cb6e1e3e5b..3f80c82288 100644
--- a/src/backend/storage/lmgr/proc.c
+++ b/src/backend/storage/lmgr/proc.c
@@ -268,6 +268,12 @@ InitProcGlobal(void)
 
 		/* Initialize lockGroupMembers list. */
 		dlist_init(&procs[i].lockGroupMembers);
+
+		/*
+		 * Initialize the atomic variable, otherwise, it won't be safe to
+		 * access it for backends that aren't currently in use.
+		 */
+		pg_atomic_init_u32(&(procs[i].procArrayGroupNext), INVALID_PGPROCNO);
 	}
 
 	/*
@@ -401,7 +407,7 @@ InitProcess(void)
 	/* Initialize fields for group XID clearing. */
 	MyProc->procArrayGroupMember = false;
 	MyProc->procArrayGroupMemberXid = InvalidTransactionId;
-	pg_atomic_init_u32(&MyProc->procArrayGroupNext, INVALID_PGPROCNO);
+	Assert(pg_atomic_read_u32(&MyProc->procArrayGroupNext) == INVALID_PGPROCNO);
 
 	/* Check that group locking fields are in a proper initial state. */
 	Assert(MyProc->lockGroupLeader == NULL);