diff --git a/freecad/gears/timinggear_t.py b/freecad/gears/timinggear_t.py
index 95ecca4..d42a639 100644
--- a/freecad/gears/timinggear_t.py
+++ b/freecad/gears/timinggear_t.py
@@ -19,6 +19,7 @@
 
 import numpy as np
 import scipy as sp
+from scipy import optimize
 
 from freecad import app
 from freecad import part