diff --git a/Dockerfile b/Dockerfile
index 05323c991..8802e29ac 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM base/devel
+FROM archlinux/archlinux:base-devel-20210627.0.27153
 
 RUN pacman -Syy --noconfirm
 RUN pacman -Syu --noconfirm
diff --git a/Source/generator/OpaqueGen.cs b/Source/generator/OpaqueGen.cs
index c0e252620..4e6c9b1c6 100644
--- a/Source/generator/OpaqueGen.cs
+++ b/Source/generator/OpaqueGen.cs
@@ -106,7 +106,9 @@ public override void Generate (GenerationInfo gen_info)
 				}
 			}
 
-			bool finalizer_needed = false;
+			// GtkWidgetPath has both gtk_widget_path_unref and gtk_widget_path_free
+			// If this happens add only one and prefer unref over free
+			bool disposeUnmanagedFuncAdded = false;
 
 			if (unref != null) {
 				unref.GenerateImport (sw);
@@ -118,13 +120,18 @@ public override void Generate (GenerationInfo gen_info)
 				sw.WriteLine ("\t\t\t}");
 				sw.WriteLine ("\t\t}");
 				sw.WriteLine ();
-
+				sw.WriteLine ("\t\tprotected override Action<IntPtr> DisposeUnmanagedFunc {");
+				sw.WriteLine ("\t\t\tget {");
+				sw.WriteLine ("\t\t\t\treturn " + unref.CName + ";");
+				sw.WriteLine ("\t\t\t}");
+				sw.WriteLine ("\t\t}");
+				sw.WriteLine ();
+				disposeUnmanagedFuncAdded = true;
 				if (unref.IsDeprecated) {
 					sw.WriteLine ("\t\t[Obsolete(\"" + QualifiedName + " is now refcounted automatically\")]");
 					sw.WriteLine ("\t\tpublic void Unref () {}");
 					sw.WriteLine ();
 				}
-				finalizer_needed = true;
 			}
 
 			if (dispose != null) {
@@ -134,43 +141,22 @@ public override void Generate (GenerationInfo gen_info)
 				sw.WriteLine ("\t\t\t" + dispose.CName + " (raw);");
 				sw.WriteLine ("\t\t}");
 				sw.WriteLine ();
+				if (!disposeUnmanagedFuncAdded) {
+					sw.WriteLine ("\t\tprotected override Action<IntPtr> DisposeUnmanagedFunc {");
+					sw.WriteLine ("\t\t\tget {");
+					sw.WriteLine ("\t\t\t\treturn " + dispose.CName + ";");
+					sw.WriteLine ("\t\t\t}");
+					sw.WriteLine ("\t\t}");
+					sw.WriteLine ();
+				}
 
 				if (dispose.IsDeprecated) {
 					sw.WriteLine ("\t\t[Obsolete(\"" + QualifiedName + " is now freed automatically\")]");
 					sw.WriteLine ("\t\tpublic void " + dispose.Name + " () {}");
 					sw.WriteLine ();
 				}
-				finalizer_needed = true;
 			}
 
-			if (finalizer_needed) {
-				sw.WriteLine ("\t\tclass FinalizerInfo {");
-				sw.WriteLine ("\t\t\tIntPtr handle;");
-				sw.WriteLine ();
-				sw.WriteLine ("\t\t\tpublic FinalizerInfo (IntPtr handle)");
-				sw.WriteLine ("\t\t\t{");
-				sw.WriteLine ("\t\t\t\tthis.handle = handle;");
-				sw.WriteLine ("\t\t\t}");
-				sw.WriteLine ();
-				sw.WriteLine ("\t\t\tpublic bool Handler ()");
-				sw.WriteLine ("\t\t\t{");
-				if (dispose != null)
-					sw.WriteLine ("\t\t\t\t{0} (handle);", dispose.CName);
-				else if (unref != null)
-					sw.WriteLine ("\t\t\t\t{0} (handle);", unref.CName);
-				sw.WriteLine ("\t\t\t\treturn false;");
-				sw.WriteLine ("\t\t\t}");
-				sw.WriteLine ("\t\t}");
-				sw.WriteLine ();
-				sw.WriteLine ("\t\t~{0} ()", Name);
-				sw.WriteLine ("\t\t{");
-				sw.WriteLine ("\t\t\tif (!Owned)");
-				sw.WriteLine ("\t\t\t\treturn;");
-				sw.WriteLine ("\t\t\tFinalizerInfo info = new FinalizerInfo (Handle);");
-				sw.WriteLine ("\t\t\tGLib.Timeout.Add (50, new GLib.TimeoutHandler (info.Handler));");
-				sw.WriteLine ("\t\t}");
-				sw.WriteLine ();
-			}
 
 #if false
 			Method copy = Methods ["Copy"] as Method;
diff --git a/Source/glib/Opaque.cs b/Source/glib/Opaque.cs
index 955285f6a..2955ae8b0 100644
--- a/Source/glib/Opaque.cs
+++ b/Source/glib/Opaque.cs
@@ -81,14 +81,78 @@ protected IntPtr Raw {
 					Ref (_obj);
 				}
 			}
-		}       
+		}
+
+		#region IDisposable implementation
+		class FinalizerInfo
+		{
+			IntPtr handle;
+			Action<IntPtr> unrefFunc;
+
+			public FinalizerInfo (Action<IntPtr> unrefFunc, IntPtr handle)
+			{
+				this.handle = handle;
+				this.unrefFunc = unrefFunc;
+			}
+
+			public bool Handler ()
+			{
+				unrefFunc (handle);
+				return false;
+			}
+		}
 
-		public virtual void Dispose ()
+		~Opaque ()
+		{
+			Dispose (false);
+		}
+
+		public void Dispose ()
 		{
 			Raw = IntPtr.Zero;
+			Dispose (true);
 			GC.SuppressFinalize (this);
 		}
 
+		protected void Dispose (bool disposing)
+		{
+			if (Disposed)
+				return;
+			Disposed = true;
+			if (disposing) {
+				DisposeManagedResources ();
+			}
+			DisposeUnmanagedResources ();
+		}
+
+		/// <summary>
+		/// Disposes the managed resources.
+		/// This method is intended to be overriden.
+		/// </summary>
+		protected virtual void DisposeManagedResources ()
+		{
+		}
+
+		/// <summary>
+		/// Disposes the unmanaged resources.
+		/// This method is intended to be overriden.
+		/// </summary>
+		protected virtual void DisposeUnmanagedResources ()
+		{
+			if (!Owned || DisposeUnmanagedFunc == null)
+				return;
+			FinalizerInfo info = new FinalizerInfo (DisposeUnmanagedFunc, Handle);
+			Timeout.Add (50, new TimeoutHandler (info.Handler));
+		}
+
+		protected internal bool Disposed { get; private set; } = false;
+
+		protected virtual Action<IntPtr> DisposeUnmanagedFunc { get; }
+
+		#endregion
+
+
+
 		// These take an IntPtr arg so we don't get conflicts if we need
 		// to have an "[Obsolete] public void Ref ()"