diff --git a/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/Excel/XLWorkbook_Save.cs
index 457a474..2e62631 100644
--- a/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -4698,7 +4698,7 @@
                 }
             }
 
-            if (xlWorksheet.Pictures().Count > 0)
+            if (xlWorksheet.Pictures() != null && xlWorksheet.Pictures().Count > 0)
             {
                 Drawing worksheetDrawing = new Drawing { Id = worksheetPart.GetIdOfPart(worksheetPart.DrawingsPart) };
                 worksheetDrawing.AddNamespaceDeclaration("r", "http://schemas.openxmlformats.org/officeDocument/2006/relationships");