diff --git a/py/mpz.c b/py/mpz.c
index f5675a2917..80473df882 100644
--- a/py/mpz.c
+++ b/py/mpz.c
@@ -939,10 +939,6 @@ void mpz_set_from_bytes(mpz_t *z, bool big_endian, size_t len, const byte *buf)
     z->len = mpn_remove_trailing_zeros(z->dig, z->dig + z->len);
 }
 
-bool mpz_is_zero(const mpz_t *z) {
-    return z->len == 0;
-}
-
 #if 0
 these functions are unused
 
diff --git a/py/mpz.h b/py/mpz.h
index 878febf8b4..2ff404ffa8 100644
--- a/py/mpz.h
+++ b/py/mpz.h
@@ -111,7 +111,7 @@ void mpz_set_from_float(mpz_t *z, mp_float_t src);
 size_t mpz_set_from_str(mpz_t *z, const char *str, size_t len, bool neg, unsigned int base);
 void mpz_set_from_bytes(mpz_t *z, bool big_endian, size_t len, const byte *buf);
 
-bool mpz_is_zero(const mpz_t *z);
+static inline bool mpz_is_zero(const mpz_t *z) { return z->len == 0; }
 int mpz_cmp(const mpz_t *lhs, const mpz_t *rhs);
 
 void mpz_abs_inpl(mpz_t *dest, const mpz_t *z);