diff --git a/ILSpy/TreeNodes/AssemblyTreeNode.cs b/ILSpy/TreeNodes/AssemblyTreeNode.cs
index a4e9f1c0d..59ea8b066 100644
--- a/ILSpy/TreeNodes/AssemblyTreeNode.cs
+++ b/ILSpy/TreeNodes/AssemblyTreeNode.cs
@@ -232,6 +232,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			{
 				if (ns.Children.Count > 0)
 					this.Children.Add(ns);
+				ns.SetPublicAPI(ns.Children.OfType<ILSpyTreeNode>().Any(n => n.IsPublicAPI));
 			}
 		}
 
diff --git a/ILSpy/TreeNodes/NamespaceTreeNode.cs b/ILSpy/TreeNodes/NamespaceTreeNode.cs
index c51111558..19982834f 100644
--- a/ILSpy/TreeNodes/NamespaceTreeNode.cs
+++ b/ILSpy/TreeNodes/NamespaceTreeNode.cs
@@ -29,6 +29,7 @@ namespace ICSharpCode.ILSpy.TreeNodes
 	public sealed class NamespaceTreeNode : ILSpyTreeNode
 	{
 		readonly string name;
+		bool isPublicAPI;
 
 		public string Name {
 			get { return name; }
@@ -49,6 +50,13 @@ namespace ICSharpCode.ILSpy.TreeNodes
 			get { return Images.Namespace; }
 		}
 
+		public override bool IsPublicAPI => isPublicAPI;
+
+		internal void SetPublicAPI(bool value)
+		{
+			this.isPublicAPI = value;
+		}
+
 		public override FilterResult Filter(FilterSettings settings)
 		{
 			if (settings.SearchTermMatches(name))