Fix off-by-one overwrite.
diff --git a/src/dnssec.c b/src/dnssec.c
index 0f95f4a..2d00570 100644
--- a/src/dnssec.c
+++ b/src/dnssec.c
@@ -353,7 +353,8 @@
       l[len] = '.';
     }
 
-  *(l-1) = 0;
+  if (l != name)
+    *(l-1) = 0;
 }
 
 /* Input in presentation format */