diff --git a/src/PdfSharp/Pdf.Signatures/PdfSignatureHandler.cs b/src/PdfSharp/Pdf.Signatures/PdfSignatureHandler.cs
index 1fd2844d..f0e64c93 100644
--- a/src/PdfSharp/Pdf.Signatures/PdfSignatureHandler.cs
+++ b/src/PdfSharp/Pdf.Signatures/PdfSignatureHandler.cs
@@ -129,10 +129,15 @@ private void AddSignatureComponents(object sender, EventArgs e)
             this.contentsTraker = new PositionTracker(paddedContents);
             this.rangeTracker = new PositionTracker(paddedRange);
 
-            if (!Document.Pages[0].Elements.ContainsKey(PdfPage.Keys.Annots))
-                Document.Pages[0].Elements.Add(PdfPage.Keys.Annots, new PdfArray(Document));
-
-            (Document.Pages[0].Elements[PdfPage.Keys.Annots] as PdfArray).Elements.Add(signature);
+            var annotations = Document.Pages[0].Elements.GetArray(PdfPage.Keys.Annots);
+            if (annotations == null)
+            {
+                Document.Pages[0].Elements.Add(PdfPage.Keys.Annots, new PdfArray(Document, signature));
+            }
+            else
+            {
+                annotations.Elements.Add(signature);
+            }
                         
             catalog.AcroForm.Fields.Elements.Add(signature);