--- a/setup.py
+++ b/setup.py
@@ -100,6 +100,10 @@
         w(kwd.get("end", "\n"))
 
 def endianness_macro():
+    if os.environ["CONFIG_BIG_ENDIAN"] == "y":
+        return ('PCT_BIG_ENDIAN', 1)
+    else:
+        return ('PCT_LITTLE_ENDIAN', 1)
     s = struct.pack("@I", 0x33221100)
     if s == "\x00\x11\x22\x33".encode():     # little endian
         return ('PCT_LITTLE_ENDIAN', 1)
