diff --git a/py/mpz.c b/py/mpz.c
index 2a4fb4659d..b3f8b15b60 100644
--- a/py/mpz.c
+++ b/py/mpz.c
@@ -711,7 +711,11 @@ typedef uint32_t mp_float_int_t;
 #endif
     union {
         mp_float_t f;
+        #if MP_ENDIANNESS_LITTLE
         struct { mp_float_int_t frc:MP_FLOAT_FRAC_BITS, exp:MP_FLOAT_EXP_BITS, sgn:1; } p;
+        #else
+        struct { mp_float_int_t sgn:1, exp:MP_FLOAT_EXP_BITS, frc:MP_FLOAT_FRAC_BITS; } p;
+        #endif
     } u = {src};
 
     z->neg = u.p.sgn;