Fix usage of PyUnicode_READY() in PyUnicode_GetLength()
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 3ce845c..7215517 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -2838,7 +2838,7 @@
 Py_ssize_t
 PyUnicode_GetLength(PyObject *unicode)
 {
-    if (!PyUnicode_Check(unicode) || PyUnicode_READY(unicode) != -1) {
+    if (!PyUnicode_Check(unicode) || PyUnicode_READY(unicode) == -1) {
         PyErr_BadArgument();
         return -1;
     }