diff --git a/asterix-external-data/src/main/resources/adm.grammar b/asterix-external-data/src/main/resources/adm.grammar
index 973c2b9..2626a31 100644
--- a/asterix-external-data/src/main/resources/adm.grammar
+++ b/asterix-external-data/src/main/resources/adm.grammar
@@ -47,9 +47,7 @@
 RECTANGLE_CONS = string(rectangle)
 CIRCLE_CONS    = string(circle)
 TIME_CONS      = string(time)
-INTERVAL_TIME_CONS      = string(interval-time)
-INTERVAL_DATE_CONS      = string(interval-date)
-INTERVAL_DATETIME_CONS  = string(interval-datetime)
+INTERVAL_CONS  = string(interval)
 YEAR_MONTH_DURATION_CONS = string(year-month-duration)
 DAY_TIME_DURATION_CONS   = string(day-time-duration)
 UUID_CONS      = string(uuid)