diff --git a/Misc/NEWS.d/next/Library/2026-10-19-19-33-35.gh-issue-159739.b5fbca.rst b/Misc/NEWS.d/next/Library/2026-10-19-19-33-35.gh-issue-159739.b5fbca.rst
new file mode 100644
index 00000000000000..d4a662b10d9f4f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-10-19-19-33-35.gh-issue-159739.b5fbca.rst
@@ -0,0 +1 @@
+Fix a memory leak when Unicode normalization cannot grow its temporary buffer.
diff --git a/Modules/unicodedata.c b/Modules/unicodedata.c
index 60011f2ec84eb3..9bd3639d9c3f41 100644
--- a/Modules/unicodedata.c
+++ b/Modules/unicodedata.c
@@ -746,7 +746,8 @@ nfd_nfkd(PyObject *self, PyObject *input, int k)
         }
 
         if (run_length > sortbuflen) {
-            Py_UCS4 *new_sortbuf = PyMem_Resize(sortbuf, Py_UCS4, run_length);
+            Py_UCS4 *new_sortbuf = sortbuf;
+            PyMem_Resize(new_sortbuf, Py_UCS4, run_length);
             if (new_sortbuf == NULL) {
                 PyErr_NoMemory();
                 PyMem_Free(sortbuf);