diff --git a/library/bignum.c b/library/bignum.c
index 0cb9505..5087308 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -761,7 +761,7 @@
             p = X->p + i;
         }
 
-        *p += c; c = ( *p < c ); i++;
+        *p += c; c = ( *p < c ); i++; p++;
     }
 
 cleanup: