diff --git a/py/mpconfig.h b/py/mpconfig.h
index f9c02a6f02..a0b6e9d485 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -187,6 +187,10 @@ typedef double mp_float_t;
 // Just because most archs are such?
 #define MP_ENDIANNESS_LITTLE (1)
 #endif
+// Ensure we don't accidentally set both endiannesses
+#if MP_ENDIANNESS_BIG
+#define MP_ENDIANNESS_LITTLE (0)
+#endif
 
 // printf format spec to use for machine_int_t and friends
 #ifndef INT_FMT