diff --git a/roberta/ev3.py b/roberta/ev3.py
index 16067b6..abd2184 100644
--- a/roberta/ev3.py
+++ b/roberta/ev3.py
@@ -526,7 +526,7 @@ def driveInCurve(self, direction, left_port, left_speed_pct, right_port, right_s
             # start motors
             ml.run_to_rel_pos()
             mr.run_to_rel_pos()
-            while (ml.state or mr.state):
+            while ((ml.state and left_speed_pct) or (mr.state and right_speed_pct)):
                 self.busyWait()
         else:
             if direction is 'backwards':