diff --git a/src/EPPlus/Core/ChangableDictionary.cs b/src/EPPlus/Core/ChangableDictionary.cs
index 7668b18cc..260f7a484 100644
--- a/src/EPPlus/Core/ChangableDictionary.cs
+++ b/src/EPPlus/Core/ChangableDictionary.cs
@@ -66,7 +66,7 @@ internal virtual void InsertAndShift(int fromPosition, int add)
                 pos = ~pos;
             }
 
-            if (pos + 1 >= _index[0].Length - 1)
+            if (_count >= _index[0].Length - 1)
             {
                 Array.Resize(ref _index[0], _index[0].Length << 1);
                 Array.Resize(ref _index[1], _index[1].Length << 1);
diff --git a/src/EPPlusTest/Issues/WorksheetIssues.cs b/src/EPPlusTest/Issues/WorksheetIssues.cs
index a7cd11ea6..13aaf0530 100644
--- a/src/EPPlusTest/Issues/WorksheetIssues.cs
+++ b/src/EPPlusTest/Issues/WorksheetIssues.cs
@@ -4,6 +4,7 @@
 using OfficeOpenXml.Drawing;
 using OfficeOpenXml.Drawing.Chart;
 using OfficeOpenXml.FormulaParsing;
+using OfficeOpenXml.FormulaParsing.Excel.Functions.Information;
 using OfficeOpenXml.FormulaParsing.Excel.Functions.Logical;
 using OfficeOpenXml.FormulaParsing.Excel.Functions.MathFunctions;
 using OfficeOpenXml.RichData;
@@ -1112,5 +1113,22 @@ public void i2258()
             Assert.AreEqual("Negative 4000,000", d3);
         }
 
+        [TestMethod]
+        public void InsertAndShift_ShouldNotThrow_WhenArrayIsFull()
+        {
+            using var package = new ExcelPackage();
+            var sheet = package.Workbook.Worksheets.Add("Sheet1");
+
+            // Fill 7 columns with formatting to trigger the boundary condition
+            for (int col = 1; col <= 7; col++)
+            {
+                sheet.Column(col).Width = 15;
+            }
+
+            // These two inserts should not throw ArgumentException
+            sheet.InsertColumn(3, 1);
+            sheet.InsertColumn(5, 1);
+        }
+
     }
 }