explicit cast
diff --git a/bn_mp_set_double.c b/bn_mp_set_double.c
index 0e230c7..f0de20c 100644
--- a/bn_mp_set_double.c
+++ b/bn_mp_set_double.c
@@ -24,7 +24,7 @@ int mp_set_double(mp_int *a, double b)
} cast;
cast.dbl = b;
- exp = (unsigned)(cast.bits >> 52) & 0x7FFU;
+ exp = (int)((unsigned)(cast.bits >> 52) & 0x7FFU);
frac = (cast.bits & ((1ULL << 52) - 1ULL)) | (1ULL << 52);
if (exp == 0x7FF) { /* +-inf, NaN */