diff --git a/src/schema/rules/sidecars/meg.yaml b/src/schema/rules/sidecars/meg.yaml
index 33d851f6af..2390766900 100644
--- a/src/schema/rules/sidecars/meg.yaml
+++ b/src/schema/rules/sidecars/meg.yaml
@@ -205,7 +205,7 @@ MEGCoordsystemDigitizedHeadPoints:
     - datatype == "meg"
     - suffix == "coordsystem"
   fields:
-    DigitizedHeadPoints: optional
+    DigitizedHeadPoints__coordsystem: optional
     DigitizedHeadPointsCoordinateSystem: optional
     DigitizedHeadPointsCoordinateUnits: optional
     DigitizedHeadPointsCoordinateSystemDescription: