Fix compilation under Windows
diff --git a/Modules/_json.c b/Modules/_json.c
index 7c5e5e4..d5120fa 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -138,6 +138,7 @@
 {
     int ret;
     Py_ssize_t nsmall;
+    PyObject *joined;
     assert(PyUnicode_Check(obj));
 
     if (PyList_Append(acc->small, obj))
@@ -152,7 +153,7 @@
      */
     if (nsmall < 100000)
         return 0;
-    PyObject *joined = join_list_unicode(acc->small);
+    joined = join_list_unicode(acc->small);
     if (joined == NULL)
         return -1;
     if (PyList_SetSlice(acc->small, 0, nsmall, NULL)) {