diff --git a/Sources/Extensions/AppKitExtension.swift b/Sources/Extensions/AppKitExtension.swift
index 6b30b76..816e7b6 100644
--- a/Sources/Extensions/AppKitExtension.swift
+++ b/Sources/Extensions/AppKitExtension.swift
@@ -66,6 +66,9 @@ public extension NSTableView {
                 return reloadData()
             }
 
+            assert(changeset.sectionChangeCount < 1,
+                   "NSTableView group rows are not yet supported, sorry.")
+
             beginUpdates()
             setData(changeset.data)
 
@@ -120,6 +123,9 @@ public extension NSCollectionView {
                 return reloadData()
             }
 
+            assert(changeset.sectionChangeCount < 1,
+                   "NSCollectionView sections are not yet supported, sorry.")
+
             animator().performBatchUpdates({
                 setData(changeset.data)