diff --git a/contrib/earthdistance/earthdistance.sql.in b/contrib/earthdistance/earthdistance.sql.in
index fdb4552f8aab630797628ebd6734bf137b151d8b..087484da5158dae95dcdd87a9e530f92f98fbae6 100644
--- a/contrib/earthdistance/earthdistance.sql.in
+++ b/contrib/earthdistance/earthdistance.sql.in
@@ -3,7 +3,8 @@
 
 DROP FUNCTION geo_distance (point, point);
 CREATE FUNCTION geo_distance (point, point) RETURNS float8
-  AS 'MODULE_PATHNAME' LANGUAGE 'c';
+  AS 'MODULE_PATHNAME' LANGUAGE 'c'
+  WITH (isstrict);
 
 SELECT geo_distance ('(1,2)'::point, '(3,4)'::point);