diff --git a/csharp/ql/lib/ext/default.model.yml b/csharp/ql/lib/ext/default.model.yml
new file mode 100644
index 00000000000..a041c1f649b
--- /dev/null
+++ b/csharp/ql/lib/ext/default.model.yml
@@ -0,0 +1,20 @@
+extensions:
+  - addsTo:
+      pack: codeql/csharp-all
+      extensible: sourceModel
+    data: []
+
+  - addsTo:
+      pack: codeql/csharp-all
+      extensible: sinkModel
+    data: []
+
+  - addsTo:
+      pack: codeql/csharp-all
+      extensible: summaryModel
+    data: []
+
+  - addsTo:
+      pack: codeql/csharp-all
+      extensible: neutralModel
+    data: []