diff --git a/Software/python/hwtest.py b/Software/python/hwtest.py
index 4a3f460..c2ae5ef 100644
--- a/Software/python/hwtest.py
+++ b/Software/python/hwtest.py
@@ -130,6 +130,7 @@ def control_thread():
 
         # Precompute as much as possible
         c = time_data[:,2]
+        e = time_data[:,1]
         np.append(c, fir_taps[1:] * e[-len(fir_taps)+1:] + iir_taps * c[-len(iir_taps):])
         motor_speed = np.array(-1, 1, 0) * base_speed