diff --git a/src/compas_fab/robots/robot.py b/src/compas_fab/robots/robot.py
index 6398540ad..f932e266e 100644
--- a/src/compas_fab/robots/robot.py
+++ b/src/compas_fab/robots/robot.py
@@ -1415,9 +1415,7 @@ def plan_cartesian_motion(self, waypoints, start_configuration=None, group=None,
                 else:
                     cp.scale(1.0 / self.scale_factor)
                 path_constraints_WCF_scaled.append(cp)
-        else:
-            path_constraints_WCF_scaled = None
-        options["path_constraints"] = path_constraints_WCF_scaled
+            options["path_constraints"] = path_constraints_WCF_scaled
 
         # =====================
         # Attached CM and Tools
diff --git a/tests/backends/kinematics/test_inverse_kinematics.py b/tests/backends/kinematics/test_inverse_kinematics.py
index aa92f7b9a..c3e27fc18 100644
--- a/tests/backends/kinematics/test_inverse_kinematics.py
+++ b/tests/backends/kinematics/test_inverse_kinematics.py
@@ -150,4 +150,6 @@ def test_kinematics_cartesian_with_tool_coordinate_frame(frame_waypoints):
         # Assert that the trajectory is complete
         assert trajectory.fraction == 1.0
         # Assert that the trajectory has the correct number of points
+        # NOTE: At the moment the AnalyticalPyBulletClient does not perform any interpolation between frames
+        # NOTE: if future implementation fixes this, the following test will not be valid anymore
         assert len(trajectory.points) == len(frame_waypoints.target_frames)