diff --git a/ApplicationLibCode/ProjectDataModel/CellFilters/RimPolygonFilter.h b/ApplicationLibCode/ProjectDataModel/CellFilters/RimPolygonFilter.h
index 52a63e5da1..6432c2adfe 100644
--- a/ApplicationLibCode/ProjectDataModel/CellFilters/RimPolygonFilter.h
+++ b/ApplicationLibCode/ProjectDataModel/CellFilters/RimPolygonFilter.h
@@ -30,6 +30,7 @@ class RimPolygon;
 class RigGridBase;
 class RigFemPartGrid;
 class RimPolygonInView;
+class RigEclipseCaseData;
 
 namespace cvf
 {