diff --git a/src/universe.cpp b/src/universe.cpp
index b5d33ac9a2..c2a6754fac 100644
--- a/src/universe.cpp
+++ b/src/universe.cpp
@@ -164,6 +164,8 @@ void Universe::add_world(char *str)
   char *ptr;
 
   n = 1;
+  nper = 0;
+
   if (str != NULL) {
 
     // check for valid partition argument