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..fcc92611c 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 ()
 		{
@@ -78,6 +79,10 @@ public void DefineConstant2 (string name, object value, int sigToken)
 
 		public void Close ()
 		{
+			if (closed)
+				return;
+
+			closed = true;
 			writer.Close ();
 			Marshal.ReleaseComObject (writer);