diff --git a/stl/utils.py b/stl/utils.py
index 3a2b938..f7d9a1e 100644
--- a/stl/utils.py
+++ b/stl/utils.py
@@ -121,6 +121,5 @@ def to_mtl(phi):
 
 
 def from_mtl(phi, ap_map):
-    focus = lineq_lens(phi)
+    focus = AP_lens(phi)
     return focus.modify(ap_map.get)
-