diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 305289b..758d054 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -2044,7 +2044,7 @@
 {
     PyObject *v;
     /* It might be possible to tighten this worst case */
-    Py_ssize_t allocated = 5 * size;
+    Py_ssize_t allocated = 8 * size;
     int inShift = 0;
     Py_ssize_t i = 0;
     unsigned int base64bits = 0;
@@ -2055,7 +2055,7 @@
     if (size == 0)
         return PyBytes_FromStringAndSize(NULL, 0);
 
-    if (allocated / 5 != size)
+    if (allocated / 8 != size)
         return PyErr_NoMemory();
 
     v = PyBytes_FromStringAndSize(NULL, allocated);