diff --git a/Revit_Core_Engine/Query/OpeningSurface.cs b/Revit_Core_Engine/Query/OpeningSurface.cs
index 538389613..75797c4d4 100644
--- a/Revit_Core_Engine/Query/OpeningSurface.cs
+++ b/Revit_Core_Engine/Query/OpeningSurface.cs
@@ -310,7 +310,7 @@ private static List<ISurface> GetOpeningGeometry(Transaction t, Document doc, Li
             t.RollBack(failureHandlingOptions);
 
             if (loops != null)
-                surfaces.AddRange(loops.Select(x => new PlanarSurface(x.FromRevit(), null)));
+                surfaces.AddRange(loops.Select(x => new PlanarSurface(x.FromRevit(), new List<ICurve>())));
             else if (surfaces.Count != 0)
                 BH.Engine.Base.Compute.RecordWarning(String.Format("Geometrical processing of a Revit element failed due to an internal Revit error. Converted opening might be missing one or more of its surfaces. Revit ElementId: {0}", familyInstance.Id));
 
diff --git a/Revit_Core_Engine/Query/PanelSurfaces.cs b/Revit_Core_Engine/Query/PanelSurfaces.cs
index 4c1911ce7..d6f16cf0e 100644
--- a/Revit_Core_Engine/Query/PanelSurfaces.cs
+++ b/Revit_Core_Engine/Query/PanelSurfaces.cs
@@ -292,11 +292,11 @@ private static Dictionary<ElementId, Dictionary<PlanarSurface, List<PlanarSurfac
                                 }
 
                                 CurveLoop outline = loops.FirstOrDefault(x => x.IsCounterclockwise(plane.Normal));
-                                PlanarSurface surface = new PlanarSurface(outline.FromRevit(), null);
+                                PlanarSurface surface = new PlanarSurface(outline.FromRevit(), new List<ICurve>());
                                 List<PlanarSurface> openings = new List<PlanarSurface>();
                                 foreach (CurveLoop loop in loops.Where(x => x != outline))
                                 {
-                                    openings.Add(new PlanarSurface(loop.FromRevit(), null));
+                                    openings.Add(new PlanarSurface(loop.FromRevit(), new List<ICurve>()));
                                 }
 
                                 if (insertsDeleted[id])
@@ -319,7 +319,7 @@ private static Dictionary<ElementId, Dictionary<PlanarSurface, List<PlanarSurfac
                                             {
                                                 foreach (CurveLoop cl in pf.GetEdgesAsCurveLoops())
                                                 {
-                                                    openings.Add(new PlanarSurface(cl.FromRevit(), null));
+                                                    openings.Add(new PlanarSurface(cl.FromRevit(), new List<ICurve>()));
                                                 }
                                             }
                                         }