1 files changed, 8 insertions, 4 deletions
diff --git a/add.c b/add.c
index 6e75eac51..9af0c3543 100644
--- a/add.c
+++ b/add.c
@@ -294,8 +294,11 @@ mpfr_add1 (a, b, c, rnd_mode, diff_exp)
         if (difs)
         {
           cc = cprev << (BITS_PER_MP_LIMB - difs);
-          cprev = cp[--ck];
-          cc += cprev >> difs;
+	  if (ck > 0)
+	    {
+	      cprev = cp[--ck];
+	      cc += cprev >> difs;
+	    }
         }
         else
           cc = cp[--ck];
@@ -338,9 +341,9 @@ mpfr_add1 (a, b, c, rnd_mode, diff_exp)
           if (ck < 0)
             goto c_read;
           cc = cprev << (BITS_PER_MP_LIMB - difs);
-          if (--ck >= 0)
+          if (ck > 0)
           {
-            cprev = cp[ck];
+            cprev = cp[--ck];
             cc += cprev >> difs;
           }
         }
@@ -389,6 +392,7 @@ mpfr_add1 (a, b, c, rnd_mode, diff_exp)
         fb = 1;
         goto rounding;
       }
+      MPFR_ASSERTN(ck >= 0);
       while (ck)
       {
         if (cp[--ck])