diff -r 1002a1bdc5b1 Objects/bytesobject.c
--- a/Objects/bytesobject.c	Sun Aug 07 10:19:20 2016 -0700
+++ b/Objects/bytesobject.c	Mon Aug 08 04:15:08 2016 +0900
@@ -2563,21 +2563,23 @@
         return NULL;
     }
     /* Is it an integer? */
-    size = PyNumber_AsSsize_t(x, PyExc_OverflowError);
-    if (size == -1 && PyErr_Occurred()) {
-        if (PyErr_ExceptionMatches(PyExc_OverflowError))
+    if (PyIndex_Check(x)) {
+        size = PyNumber_AsSsize_t(x, PyExc_OverflowError);
+        if (size == -1 && PyErr_Occurred()) {
+            if (PyErr_ExceptionMatches(PyExc_OverflowError))
+                return NULL;
+            PyErr_Clear();  // Fallback to below
+        }
+        else if (size < 0) {
+            PyErr_SetString(PyExc_ValueError, "negative count");
             return NULL;
-        PyErr_Clear();
-    }
-    else if (size < 0) {
-        PyErr_SetString(PyExc_ValueError, "negative count");
-        return NULL;
-    }
-    else {
-        new = _PyBytes_FromSize(size, 1);
-        if (new == NULL)
-            return NULL;
-        return new;
+        }
+        else {
+            new = _PyBytes_FromSize(size, 1);
+            if (new == NULL)
+                return NULL;
+            return new;
+        }
     }
 
     return PyBytes_FromObject(x);