diff --git a/RhSolutions.AddIn/Services/ExcelWriter.cs b/RhSolutions.AddIn/Services/ExcelWriter.cs
index ed4e2e0..4ac4f2b 100644
--- a/RhSolutions.AddIn/Services/ExcelWriter.cs
+++ b/RhSolutions.AddIn/Services/ExcelWriter.cs
@@ -110,7 +110,7 @@ public class ExcelWriter : IWriter, IDisposable
         Range worksheetCells = _worksheet.Cells;
         Range skuColumn = _skuCell.EntireColumn;
 
-        int? row = GetPositionRow(skuColumn, positionAmount.Key.ProductSku.ToString(), positionAmount.Key.ProductLines.First());
+        int? row = GetPositionRow(skuColumn, positionAmount.Key.ProductSku.ToString(), positionAmount.Key.ProductLines.FirstOrDefault());
 
         if (row != null)
         {
@@ -126,7 +126,7 @@ public class ExcelWriter : IWriter, IDisposable
 
         if (_oldSkuCell != null)
         {
-            row = GetPositionRow(_oldSkuCell.EntireColumn, positionAmount.Key.ProductSku.ToString(), positionAmount.Key.ProductLines.First());
+            row = GetPositionRow(_oldSkuCell.EntireColumn, positionAmount.Key.ProductSku.ToString(), positionAmount.Key.ProductLines.FirstOrDefault());
 
             if (row != null)
             {
@@ -142,7 +142,7 @@ public class ExcelWriter : IWriter, IDisposable
         }
 
         string sku = positionAmount.Key.ProductSku.Article;
-        row = GetPositionRow(skuColumn, sku, positionAmount.Key.ProductLines.First());
+        row = GetPositionRow(skuColumn, sku, positionAmount.Key.ProductLines.FirstOrDefault());
 
         if (row != null)
         {