diff --git a/starttree.h b/starttree.h
index 74a6573..fc1c7b3 100644
--- a/starttree.h
+++ b/starttree.h
@@ -388,7 +388,7 @@ namespace StartTree
         Builder(const char* nameToUse, const char *descriptionToGive)
         : name(nameToUse), description(descriptionToGive), silent(false)
         , isOutputToBeAppended(false), isOutputToBeZipped(false)
-        , precision(6), subtreeOnly(false) {
+        , precision(6), isRooted(false), subtreeOnly(false) {
         }
 
         /**