diff --git a/src/lib/Radio/readsky.c b/src/lib/Radio/readsky.c
index f30553b..b340d41 100644
--- a/src/lib/Radio/readsky.c
+++ b/src/lib/Radio/readsky.c
@@ -686,8 +686,10 @@ printf("Nc=%d\n",Nc);
     memset(buf,0,buff_len);
     c=read_next_string(&buf,&buff_len,cfp);
     if (c!=1) {
-     /* first column is solution number (int) 1..8N */
+     /* first column is solution number (int) 0..8N-1 */
      sscanf(buf,"%d",&cn);
+     /* also do a sanity check */
+     if ( cn<0 || cn>Nc ) cn=0;
     }
 #ifdef DEBUG
     printf("%d ",cn);