diff --git a/gmp-impl.h b/gmp-impl.h
index e91e18cb..240c705e 100644
--- a/gmp-impl.h
+++ b/gmp-impl.h
@@ -974,11 +974,21 @@ __GMP_DECLSPEC extern gmp_randstate_t  __gmp_rands;
    fastest hardware currently (2003) would need 100 million years, which
    suggests that these limits are acceptable.  */
 #if WANT_FFT
+#if HAVE_NATIVE_mpn_sublsh1_n
 #define MPN_TOOM3_MUL_N_TSIZE(n)  (2*(n) + 63)
 #define MPN_TOOM3_SQR_N_TSIZE(n)  (2*(n) + 63)
+#else
+#define MPN_TOOM3_MUL_N_TSIZE(n)  (2*(n) + 2*(n/3) + 63)
+#define MPN_TOOM3_SQR_N_TSIZE(n)  (2*(n) + 2*(n/3) + 63)
+#endif
 #else /* WANT_FFT */
+#if HAVE_NATIVE_mpn_sublsh1_n
 #define MPN_TOOM3_MUL_N_TSIZE(n)  (2*(n) + 255)
 #define MPN_TOOM3_SQR_N_TSIZE(n)  (2*(n) + 255)
+#else
+#define MPN_TOOM3_MUL_N_TSIZE(n)  (2*(n) + 2*(n/3) + 255)
+#define MPN_TOOM3_SQR_N_TSIZE(n)  (2*(n) + 2*(n/3) + 255)
+#endif
 #define MPN_TOOM3_MAX_N 285405
 #endif /* WANT_FFT */
 
diff --git a/mpz/set_d.c b/mpz/set_d.c
index d14cf00b..8f5169eb 100644
--- a/mpz/set_d.c
+++ b/mpz/set_d.c
@@ -56,9 +56,6 @@ mpz_set_d (mpz_ptr r, double d)
   if (ALLOC(r) < rn)
     _mpz_realloc (r, rn);
 
-  if (rn <= 0)
-      rn = 0;
-
   rp = PTR (r);
 
   switch (rn)