diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 03ca079..25958aa 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -908,6 +908,37 @@ RecordNewMultiXact(MultiXactId multi, MultiXactOffset offset,
 }
 
 /*
+ * Check if we could add "distance" to "start", without moving past
+ * "boundary", using modulo arithmetic.
+ */
+static bool
+MultiXactOffsetWouldWrap(MultiXactOffset boundary,
+						 MultiXactOffset start,
+						 int distance)
+{
+	MultiXactOffset finish = start + distance;
+	Assert(distance >= 0);
+	if (start < boundary)
+		/*
+		 *  <----S----B---->
+		 *
+		 *  [---)            = F wrapped past B (and UINT_MAX)
+		 *       [---)       = F OK
+		 *            [----] = F wrapped past B
+		 */
+		return finish >= boundary || finish < start;
+	else
+		/*
+		 *  <----B----S---->
+		 *
+		 *  [---)            = F OK
+		 *       [---)       = F wrapped past B (and UINT_MAX)
+		 *            [----] = F OK
+		 */
+		return finish >= boundary && finish < start;
+}
+
+/*
  * GetNewMultiXactId
  *		Get the next MultiXactId.
  *
@@ -1063,13 +1094,13 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset)
 	 * multixact freeze settings would have to be reduced for that to have any
 	 * effect, and we can't do that from here.
 	 */
-	if (MultiXactOffsetPrecedes(MultiXactState->offsetStopLimit, nextOffset + nmembers))
+	if (MultiXactOffsetWouldWrap(MultiXactState->offsetStopLimit, nextOffset, nmembers))
 		ereport(ERROR,
 				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
 				 errmsg("database is not accepting commands that generate new MultiXactIds to avoid \"members\" wraparound data loss in database with OID %u",
 						MultiXactState->oldestMultiXactDB),
 				 errhint("Execute a database-wide VACUUM in that database, with reduced vacuum_multixact_freeze_min_age and vacuum_multixact_freeze_table_age settings.")));
-	else if (MultiXactOffsetPrecedes(MultiXactState->offsetWarnLimit, nextOffset + nmembers))
+	else if (MultiXactOffsetWouldWrap(MultiXactState->offsetWarnLimit, nextOffset, nmembers))
 		ereport(WARNING,
 				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
 				 errmsg_plural("database with OID %u must be vacuumed before %d more multixact member is used",