diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 866fdd5af8..c38f88dba7 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -3120,8 +3120,16 @@ timestamp_pl_interval(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 						 errmsg("timestamp out of range")));
 
-			/* Add days by converting to and from Julian */
-			julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) + span->day;
+			/*
+			 * Add days by converting to and from Julian.  We need an overflow
+			 * check here since j2date expects a non-negative integer input.
+			 */
+			julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
+			if (pg_add_s32_overflow(julian, span->day, &julian) ||
+				julian < 0)
+				ereport(ERROR,
+						(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+						 errmsg("timestamp out of range")));
 			j2date(julian, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
 
 			if (tm2timestamp(tm, fsec, NULL, &timestamp) != 0)
@@ -3256,8 +3264,19 @@ timestamptz_pl_interval_internal(TimestampTz timestamp,
 						(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 						 errmsg("timestamp out of range")));
 
-			/* Add days by converting to and from Julian */
-			julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) + span->day;
+			/*
+			 * Add days by converting to and from Julian.  We need an overflow
+			 * check here since j2date expects a non-negative integer input.
+			 * In practice though, it will give correct answers for small
+			 * negative Julian dates; we should allow -1 to avoid
+			 * timezone-dependent failures, as discussed in timestamp.h.
+			 */
+			julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
+			if (pg_add_s32_overflow(julian, span->day, &julian) ||
+				julian < -1)
+				ereport(ERROR,
+						(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+						 errmsg("timestamp out of range")));
 			j2date(julian, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
 
 			tz = DetermineTimeZoneOffset(tm, attimezone);