diff --git a/generator/Signature.cs b/generator/Signature.cs
index 9c2683ce7..156480003 100644
--- a/generator/Signature.cs
+++ b/generator/Signature.cs
@@ -148,8 +148,14 @@ namespace GtkSharp.Generation {
 			foreach (Parameter p in parms) {
 
 				result [i] = p.PassAs != "" ? p.PassAs + " " : "";
-				if (p.IsOptional && p.PassAs == String.Empty)
-					result [i++] += (p.Generatable is StructGen || p.Generatable is BoxedGen) ? (p.CSType + ".Zero") : "null";
+				if (p.IsOptional && p.PassAs == String.Empty) {
+					if (p.Generatable is StructGen || p.Generatable is BoxedGen)
+						result [i++] += " .Zero";
+					else if (p.CSType == "System.IntPtr")
+						result [i++] += "System.IntPtr.Zero";
+					else
+						result [i++] += "null";
+				}
 				else
 					result [i++] += p.Name;
 			}