diff --git a/src/libraries/System.IO.FileSystem/tests/FileStream/FileStreamConformanceTests.cs b/src/libraries/System.IO.FileSystem/tests/FileStream/FileStreamConformanceTests.cs
index 64b44242450ef4..271cb2833c94ae 100644
--- a/src/libraries/System.IO.FileSystem/tests/FileStream/FileStreamConformanceTests.cs
+++ b/src/libraries/System.IO.FileSystem/tests/FileStream/FileStreamConformanceTests.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using Microsoft.Win32.SafeHandles;
+using System.Collections.Generic;
 using System.IO.Pipes;
 using System.Linq;
 using System.Threading.Tasks;
@@ -98,6 +99,40 @@ public async Task WriteAsyncStartsWherePreviousReadAsyncHasFinished(ReadWriteMod
             byte[] allBytes = File.ReadAllBytes(filePath);
             Assert.Equal(initialData.Concat(writeBuffer), allBytes);
         }
+
+        [Theory]
+        [MemberData(nameof(AllReadWriteModes))]
+        public async Task NoDataIsLostWhenWritingToFile(ReadWriteMode mode)
+        {
+            string filePath;
+            List<byte> writtenBytes = new List<byte>();
+
+            using (FileStream stream = (FileStream)await CreateWriteOnlyStreamCore(Array.Empty<byte>()))
+            {
+                filePath = stream.Name;
+
+                // the following buffer fits into internal FileStream buffer
+                byte[] small = Enumerable.Repeat(byte.MinValue, BufferSize - 1).ToArray();
+                // the following buffer does not fit into internal FileStream buffer
+                byte[] big = Enumerable.Repeat(byte.MaxValue, BufferSize + 1).ToArray();
+                // in this test we are selecting a random buffer and write it to file
+                // the goal is to cover all possible scenarios for the internal buffering logic
+                Random random = new Random(12345);
+                for (int i = 0; i < 1000; i++)
+                {
+                    byte[] bytes = random.Next() % 2 == 0 ? small : big;
+
+                    await WriteAsync(mode, stream, bytes, 0, bytes.Length);
+
+                    writtenBytes.AddRange(bytes);
+                    Assert.Equal(writtenBytes.Count, stream.Length);
+                    Assert.Equal(stream.Length, stream.Position);
+                }
+            }
+
+            byte[] allBytes = File.ReadAllBytes(filePath);
+            Assert.Equal(writtenBytes.ToArray(), allBytes);
+        }
     }
 
     public class UnbufferedSyncFileStreamStandaloneConformanceTests : FileStreamStandaloneConformanceTests
diff --git a/src/libraries/System.Private.CoreLib/src/System/IO/Strategies/BufferedFileStreamStrategy.cs b/src/libraries/System.Private.CoreLib/src/System/IO/Strategies/BufferedFileStreamStrategy.cs
index b2a239b20b73bc..2b914e7bc0aec1 100644
--- a/src/libraries/System.Private.CoreLib/src/System/IO/Strategies/BufferedFileStreamStrategy.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/IO/Strategies/BufferedFileStreamStrategy.cs
@@ -539,6 +539,10 @@ private void WriteSpan(ReadOnlySpan<byte> source, ArraySegment<byte> arraySegmen
                         source.Slice(0, numBytes).CopyTo(_buffer!.AsSpan(_writePos));
                         _writePos += numBytes;
                         source = source.Slice(numBytes);
+                        if (arraySegment.Array != null)
+                        {
+                            arraySegment = arraySegment.Slice(numBytes);
+                        }
                     }
                 }