diff --git a/src/libraries/System.Private.CoreLib/src/System/IO/BufferedStream.cs b/src/libraries/System.Private.CoreLib/src/System/IO/BufferedStream.cs
index 40abcbdac5580a..09aa09d3446056 100644
--- a/src/libraries/System.Private.CoreLib/src/System/IO/BufferedStream.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/IO/BufferedStream.cs
@@ -1166,9 +1166,12 @@ private void WriteByteSlow(byte value)
                 EnsureBufferAllocated();
             }
 
-            // We should not be flushing here, but only writing to the underlying stream, but previous version flushed, so we keep this.
             if (_writePos >= _bufferSize - 1)
-                FlushWrite();
+            {
+                Debug.Assert(_stream != null);
+                _stream.Write(_buffer!, 0, _writePos);
+                _writePos = 0;
+            }
 
             _buffer![_writePos++] = value;