diff --git a/ClosedXML_Tests/Utils/PackageHelper.cs b/ClosedXML_Tests/Utils/PackageHelper.cs
index 3def760..cb4bd3f 100644
--- a/ClosedXML_Tests/Utils/PackageHelper.cs
+++ b/ClosedXML_Tests/Utils/PackageHelper.cs
@@ -346,14 +346,22 @@
                 }
                 var leftPart = left.GetPart(pair.Uri);
                 var rightPart = right.GetPart(pair.Uri);
-                using (Stream oneStream = leftPart.GetStream(FileMode.Open, FileAccess.Read))
-                using (Stream otherStream = rightPart.GetStream(FileMode.Open, FileAccess.Read))
+                using (Stream leftPackagePartStream = leftPart.GetStream(FileMode.Open, FileAccess.Read))
+                using (Stream rightPackagePartStream = rightPart.GetStream(FileMode.Open, FileAccess.Read))
+                using (var leftMemoryStream = new MemoryStream())
+                using (var rightMemoryStream = new MemoryStream())
                 {
+                    leftPackagePartStream.CopyTo(leftMemoryStream);
+                    rightPackagePartStream.CopyTo(rightMemoryStream);
+
+                    leftMemoryStream.Seek(0, SeekOrigin.Begin);
+                    rightMemoryStream.Seek(0, SeekOrigin.Begin);
+
                     bool stripColumnWidthsFromSheet = stripColumnWidths &&
                         leftPart.ContentType == @"application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml" &&
                         rightPart.ContentType == @"application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml";
 
-                    if (!StreamHelper.Compare(oneStream, otherStream, stripColumnWidthsFromSheet))
+                    if (!StreamHelper.Compare(leftMemoryStream, rightMemoryStream, stripColumnWidthsFromSheet))
                     {
                         pair.Status = CompareStatus.NonEqual;
                         if (compareToFirstDifference)
@@ -507,4 +515,4 @@
 
         //--
     }
-}
\ No newline at end of file
+}