diff --git a/Doc/library/_thread.rst b/Doc/library/_thread.rst
index a787e2f..7122861 100644
--- a/Doc/library/_thread.rst
+++ b/Doc/library/_thread.rst
@@ -93,7 +93,8 @@
    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
+   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
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index 5269994..c56d707 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -89,7 +89,8 @@
    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
+   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
diff --git a/Misc/ACKS b/Misc/ACKS
index 483e96c..4a24cc3 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -914,6 +914,7 @@
 Simon Mathieu
 Laura Matson
 Graham Matthews
+mattip
 Martin Matusiak
 Dieter Maurer
 Daniel May
diff --git a/Misc/NEWS b/Misc/NEWS
index 9b455ab..38f31e4 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -64,6 +64,9 @@
 Documentation
 -------------
 
+- Issue #24952: Clarify the default size argument of stack_size() in
+  the "threading" and "_thread" modules. Patch from Mattip.
+
 Tests
 -----