diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index e69bf01..df10888 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -15669,13 +15669,13 @@
         }
         switch (PyUnicode_CHECK_INTERNED(s)) {
         case SSTATE_INTERNED_IMMORTAL:
-            Py_REFCNT(s) += 1;
+            Py_SET_REFCNT(s, Py_REFCNT(s) + 1);
 #ifdef INTERNED_STATS
             immortal_size += PyUnicode_GET_LENGTH(s);
 #endif
             break;
         case SSTATE_INTERNED_MORTAL:
-            Py_REFCNT(s) += 2;
+            Py_SET_REFCNT(s, Py_REFCNT(s) + 2);
 #ifdef INTERNED_STATS
             mortal_size += PyUnicode_GET_LENGTH(s);
 #endif