diff --git a/symbols/pdb/Mono.Cecil.Pdb/NativePdbWriter.cs b/symbols/pdb/Mono.Cecil.Pdb/NativePdbWriter.cs
index 7bb9c6f15..9597d7fa4 100644
--- a/symbols/pdb/Mono.Cecil.Pdb/NativePdbWriter.cs
+++ b/symbols/pdb/Mono.Cecil.Pdb/NativePdbWriter.cs
@@ -267,6 +267,7 @@ public void Write ()
 
 		public void Dispose ()
 		{
+			writer.Close ();
 		}
 	}
 
diff --git a/symbols/pdb/Mono.Cecil.Pdb/SymWriter.cs b/symbols/pdb/Mono.Cecil.Pdb/SymWriter.cs
index f309f2f6c..68bbfa90d 100644
--- a/symbols/pdb/Mono.Cecil.Pdb/SymWriter.cs
+++ b/symbols/pdb/Mono.Cecil.Pdb/SymWriter.cs
@@ -30,6 +30,7 @@ static extern int CoCreateInstance (
 
 		readonly ISymUnmanagedWriter2 writer;
 		readonly Collection<ISymUnmanagedDocumentWriter> documents;
+		bool closed = false;
 
 		public SymWriter ()
 		{
@@ -78,11 +79,14 @@ public void DefineConstant2 (string name, object value, int sigToken)
 
 		public void Close ()
 		{
-			writer.Close ();
-			Marshal.ReleaseComObject (writer);
+			if( !closed ) {
+				closed = true;
+				writer.Close ();
+				Marshal.ReleaseComObject ( writer );
 
-			foreach (var document in documents)
-				Marshal.ReleaseComObject (document);
+				foreach( var document in documents )
+					Marshal.ReleaseComObject ( document );
+			}
 		}
 
 		public void CloseMethod ()