diff --git a/src/Kinematics/Joint.idr b/src/Kinematics/Joint.idr
index d177c49..2adb5a1 100644
--- a/src/Kinematics/Joint.idr
+++ b/src/Kinematics/Joint.idr
@@ -41,7 +41,7 @@ public export
 record Joint n where
   constructor MkJoint
   ty : JointType n
-  l, u : Double
+  lower, upper : Double
 
 
 ||| Calculate the homogeneous matrix generated by a joint given an