diff -r 55bd86b0e333 Doc/library/_thread.rst
--- a/Doc/library/_thread.rst	Sun Aug 30 09:15:36 2015 -0700
+++ b/Doc/library/_thread.rst	Sun Aug 30 22:21:16 2015 +0300
@@ -93,8 +93,9 @@
    Return the thread stack size used when creating new threads.  The optional
    *size* argument specifies the stack size to be used for subsequently created
    threads, and must be 0 (use platform or configured default) or a positive
-   integer value of at least 32,768 (32 KiB). If changing the thread stack size is
-   unsupported, a :exc:`RuntimeError` is raised.  If the specified stack size is
+   integer value of at least 32,768 (32 KiB). If size is not specified, 0 is
+   used.  If changing the thread stack size is unsupported, a
+   :exc:`RuntimeError` is raised.  If the specified stack size is
    invalid, a :exc:`ValueError` is raised and the stack size is unmodified.  32 KiB
    is currently the minimum supported stack size value to guarantee sufficient
    stack space for the interpreter itself.  Note that some platforms may have
diff -r 55bd86b0e333 Doc/library/threading.rst
--- a/Doc/library/threading.rst	Sun Aug 30 09:15:36 2015 -0700
+++ b/Doc/library/threading.rst	Sun Aug 30 22:21:16 2015 +0300
@@ -89,8 +89,9 @@
    Return the thread stack size used when creating new threads.  The optional
    *size* argument specifies the stack size to be used for subsequently created
    threads, and must be 0 (use platform or configured default) or a positive
-   integer value of at least 32,768 (32 KiB). If changing the thread stack size is
-   unsupported, a :exc:`RuntimeError` is raised.  If the specified stack size is
+   integer value of at least 32,768 (32 KiB). If size is not specified, 0 is
+   used.  If changing the thread stack size is unsupported, a
+   :exc:`RuntimeError` is raised.  If the specified stack size is
    invalid, a :exc:`ValueError` is raised and the stack size is unmodified.  32 KiB
    is currently the minimum supported stack size value to guarantee sufficient
    stack space for the interpreter itself.  Note that some platforms may have