diff --git a/lslopt/lslfoldconst.py b/lslopt/lslfoldconst.py
index 3f53bcb..7c98bac 100644
--- a/lslopt/lslfoldconst.py
+++ b/lslopt/lslfoldconst.py
@@ -1049,7 +1049,7 @@ class foldconst(object):
         if nt in ('VECTOR', 'ROTATION', 'LIST'):
             isconst = True
             issef = True
-            for idx in xrange(len(child)-1, -1, -1):
+            for idx in xrange(len(child)):
                 self.FoldTree(child, idx)
                 if child[idx]['nt'] != 'CONST':
                     isconst = False