diff --git a/src/experimental/_impl/_sum_impl.scad b/src/experimental/_impl/_sum_impl.scad
index 2c2bc47b..7acb2a8d 100644
--- a/src/experimental/_impl/_sum_impl.scad
+++ b/src/experimental/_impl/_sum_impl.scad
@@ -1,2 +1,2 @@
 function _sum_impl(lt, leng, i = 0) =
-    i == leng - 1 ? lt[i] : (lt[i] + _sum_impl(lt, leng, i + 1));
+    i >= leng - 1 ? lt[i] : (lt[i] + _sum_impl(lt, leng, i + 1));