Index: Python/marshal.c
===================================================================
--- Python/marshal.c	(revision 75155)
+++ Python/marshal.c	(working copy)
@@ -66,6 +66,7 @@
 	Py_ssize_t size, newsize;
 	if (p->str == NULL)
 		return; /* An error already occurred */
+        Py_BEGIN_ALLOW_THREADS
 	size = PyString_Size(p->str);
 	newsize = size + size + 1024;
 	if (newsize > 32*1024*1024) {
@@ -80,6 +81,7 @@
 			PyString_AS_STRING((PyStringObject *)p->str) + newsize;
 		*p->ptr++ = Py_SAFE_DOWNCAST(c, int, char);
 	}
+        Py_END_ALLOW_THREADS
 }
 
 static void