diff --git a/libraries/stdlib/src/kotlin/io/Constants.kt b/libraries/stdlib/src/kotlin/io/Constants.kt
index 2832a0fca2b..23b37de5fa1 100644
--- a/libraries/stdlib/src/kotlin/io/Constants.kt
+++ b/libraries/stdlib/src/kotlin/io/Constants.kt
@@ -6,7 +6,10 @@ package kotlin.io
 /**
  * Returns the default buffer size when working with buffered streams.
 */
-public val defaultBufferSize: Int = 64 * 1024
+public val DEFAULT_BUFFER_SIZE: Int = 64 * 1024
+
+@Deprecated("Use DEFAULT_BUFFER_SIZE constant instead.", ReplaceWith("kotlin.io.DEFAULT_BUFFER_SIZE"))
+public val defaultBufferSize: Int = DEFAULT_BUFFER_SIZE
 
 /**
  * Returns the default block size for forEachBlock().
diff --git a/libraries/stdlib/src/kotlin/io/IOStreams.kt b/libraries/stdlib/src/kotlin/io/IOStreams.kt
index 60543659650..a8834a8e95c 100644
--- a/libraries/stdlib/src/kotlin/io/IOStreams.kt
+++ b/libraries/stdlib/src/kotlin/io/IOStreams.kt
@@ -62,7 +62,7 @@ public fun ByteArray.inputStream(offset: Int, length: Int) : ByteArrayInputStrea
  * Creates a buffered input stream wrapping this stream.
  * @param bufferSize the buffer size to use.
  */
-public fun InputStream.buffered(bufferSize: Int = defaultBufferSize): BufferedInputStream
+public fun InputStream.buffered(bufferSize: Int = DEFAULT_BUFFER_SIZE): BufferedInputStream
         = if (this is BufferedInputStream) this else BufferedInputStream(this, bufferSize)
 
 /** Creates a reader on this input stream using UTF-8 or the specified [charset]. */
@@ -83,7 +83,7 @@ public fun InputStream.bufferedReader(charset: String): BufferedReader = reader(
  * Creates a buffered output stream wrapping this stream.
  * @param bufferSize the buffer size to use.
  */
-public fun OutputStream.buffered(bufferSize: Int = defaultBufferSize): BufferedOutputStream
+public fun OutputStream.buffered(bufferSize: Int = DEFAULT_BUFFER_SIZE): BufferedOutputStream
         = if (this is BufferedOutputStream) this else BufferedOutputStream(this, bufferSize)
 
 /** Creates a writer on this output stream using UTF-8 or the specified [charset]. */
@@ -105,7 +105,7 @@ public fun OutputStream.bufferedWriter(charset: String): BufferedWriter = writer
  *
  * **Note** It is the caller's responsibility to close both of these resources.
  */
-public fun InputStream.copyTo(out: OutputStream, bufferSize: Int = defaultBufferSize): Long {
+public fun InputStream.copyTo(out: OutputStream, bufferSize: Int = DEFAULT_BUFFER_SIZE): Long {
     var bytesCopied: Long = 0
     val buffer = ByteArray(bufferSize)
     var bytes = read(buffer)
@@ -122,7 +122,7 @@ public fun InputStream.copyTo(out: OutputStream, bufferSize: Int = defaultBuffer
  *
  * **Note**: It is the caller's responsibility to close this stream.
  */
-public fun InputStream.readBytes(estimatedSize: Int = defaultBufferSize): ByteArray {
+public fun InputStream.readBytes(estimatedSize: Int = DEFAULT_BUFFER_SIZE): ByteArray {
     val buffer = ByteArrayOutputStream(estimatedSize)
     copyTo(buffer)
     return buffer.toByteArray()
diff --git a/libraries/stdlib/src/kotlin/io/ReadWrite.kt b/libraries/stdlib/src/kotlin/io/ReadWrite.kt
index cc667e6dcf5..23d47842d81 100644
--- a/libraries/stdlib/src/kotlin/io/ReadWrite.kt
+++ b/libraries/stdlib/src/kotlin/io/ReadWrite.kt
@@ -9,11 +9,11 @@ import java.util.NoSuchElementException
 
 
 /** Returns a buffered reader wrapping this Reader, or this Reader itself if it is already buffered. */
-public fun Reader.buffered(bufferSize: Int = defaultBufferSize): BufferedReader
+public fun Reader.buffered(bufferSize: Int = DEFAULT_BUFFER_SIZE): BufferedReader
         = if (this is BufferedReader) this else BufferedReader(this, bufferSize)
 
 /** Returns a buffered reader wrapping this Writer, or this Writer itself if it is already buffered. */
-public fun Writer.buffered(bufferSize: Int = defaultBufferSize): BufferedWriter
+public fun Writer.buffered(bufferSize: Int = DEFAULT_BUFFER_SIZE): BufferedWriter
         = if (this is BufferedWriter) this else BufferedWriter(this, bufferSize)
 
 /**
@@ -107,7 +107,7 @@ public fun Reader.readText(): String {
  * @param bufferSize size of character buffer to use in process.
  * @return number of bytes copies.
  */
-public fun Reader.copyTo(out: Writer, bufferSize: Int = defaultBufferSize): Long {
+public fun Reader.copyTo(out: Writer, bufferSize: Int = DEFAULT_BUFFER_SIZE): Long {
     var charsCopied: Long = 0
     val buffer = CharArray(bufferSize)
     var chars = read(buffer)
diff --git a/libraries/stdlib/src/kotlin/io/files/Utils.kt b/libraries/stdlib/src/kotlin/io/files/Utils.kt
index a66160e4dd2..debdbecfbe5 100644
--- a/libraries/stdlib/src/kotlin/io/files/Utils.kt
+++ b/libraries/stdlib/src/kotlin/io/files/Utils.kt
@@ -262,7 +262,7 @@ public fun File.relativePath(descendant: File): String {
  * @throws FileAlreadyExistsException if the destination file already exists and 'rewrite' argument is set to `false`.
  * @throws IOException if any errors occur while copying.
  */
-public fun File.copyTo(dst: File, overwrite: Boolean = false, bufferSize: Int = defaultBufferSize): Long {
+public fun File.copyTo(dst: File, overwrite: Boolean = false, bufferSize: Int = DEFAULT_BUFFER_SIZE): Long {
     if (!exists()) {
         throw NoSuchFileException(file = this, reason = "The source file doesn't exist")
     } else if (isDirectory()) {