diff --git a/src/lib/commands/xdump.c b/src/lib/commands/xdump.c
index 9e93a2f5..adc278a4 100644
--- a/src/lib/commands/xdump.c
+++ b/src/lib/commands/xdump.c
@@ -143,7 +143,7 @@ xdprval(struct valstr *val, char *sep)
 	break;
     default:
 	CANT_REACH();
-	pr("0");
+	pr("%snil", sep);
     }
     return " ";
 }