diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index ff22f85..a7d9e12 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -6164,12 +6164,7 @@
     kind = PyUnicode_KIND(unicode);
     data = PyUnicode_DATA(unicode);
     len = PyUnicode_GET_LENGTH(unicode);
-
-    switch(kind) {
-    case PyUnicode_1BYTE_KIND: expandsize = 4; break;
-    case PyUnicode_2BYTE_KIND: expandsize = 6; break;
-    case PyUnicode_4BYTE_KIND: expandsize = 10; break;
-    }
+    expandsize = kind * 2 + 2;
 
     if (len > PY_SSIZE_T_MAX / expandsize)
         return PyErr_NoMemory();