diff --git a/src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls b/src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls
index 531b8f3efe9..35cfc634529 100644
--- a/src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls
+++ b/src/main/resources/org/opentripplanner/apis/gtfs/schema.graphqls
@@ -1551,7 +1551,7 @@ type Itinerary {
 
     Note: Interlined/stay-seated transfers also increase the count.
     """
-    numberOfTransfers: Int
+    numberOfTransfers: Int!
 
     #
     # deprecated fields