diff --git a/Misc/NEWS.d/next/Library/2026-05-22-01-18-01.gh-issue-150207.je1B0Y.rst b/Misc/NEWS.d/next/Library/2026-05-22-01-18-01.gh-issue-150207.je1B0Y.rst
new file mode 100644
index 000000000000000..ebf57db806f62ca
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-22-01-18-01.gh-issue-150207.je1B0Y.rst
@@ -0,0 +1,4 @@
+Set a :exc:`MemoryError` via :c:func:`PyErr_NoMemory` when buffer allocation
+  fails in the tokenizer's ``_PyTokenizer_translate_newlines`` helper, so the
+  out-of-memory condition is propagated as a proper Python exception instead
+  of only being recorded in ``tok->done``.
diff --git a/Parser/tokenizer/helpers.c b/Parser/tokenizer/helpers.c
index 9542969ad3127b9..32064909ebba01f 100644
--- a/Parser/tokenizer/helpers.c
+++ b/Parser/tokenizer/helpers.c
@@ -221,6 +221,7 @@ _PyTokenizer_translate_newlines(const char *s, int exec_input, int preserve_crlf
     buf = PyMem_Malloc(needed_length);
     if (buf == NULL) {
         tok->done = E_NOMEM;
+        PyErr_NoMemory();
         return NULL;
     }
     for (current = buf; *s; s++, current++) {