diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index 4be1999..f77cfcc 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -2293,10 +2293,23 @@ static inline TimeOffset
 interval_cmp_value(const Interval *interval)
 {
 	TimeOffset	span;
+	TimeOffset timedayfraction;
+	TimeOffset timedays;
 
-	span = interval->time;
-	span += interval->month * INT64CONST(30) * USECS_PER_DAY;
-	span += interval->day * INT64CONST(24) * USECS_PER_HOUR;
+	timedays = ((int64)interval->time) / USECS_PER_DAY;
+	timedayfraction = interval->time - timedays * USECS_PER_DAY;
+
+	/* calculate span in days. this cannot overflow */
+	span = timedays;
+	span += interval->month * INT64CONST(30);
+	span += interval->day;
+
+	/* overflow check */
+	if (span > INT64CONST(0x7fffffffffffffff) / USECS_PER_DAY - 1)
+		ereport(ERROR,
+			  (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+			   errmsg ("interval out of range during comparison")));
+	span = span * USECS_PER_DAY + timedayfraction;
 
 	return span;
 }
@@ -2304,6 +2317,7 @@ interval_cmp_value(const Interval *interval)
 static int
 interval_cmp_internal(Interval *interval1, Interval *interval2)
 {
+	
 	TimeOffset	span1 = interval_cmp_value(interval1);
 	TimeOffset	span2 = interval_cmp_value(interval2);