diff --git a/src/qibolab/serialize.py b/src/qibolab/serialize.py
index 1136d36af..5f7dd2ff2 100644
--- a/src/qibolab/serialize.py
+++ b/src/qibolab/serialize.py
@@ -23,7 +23,7 @@
     QubitPairMap,
     Settings,
 )
-from qibolab.pulses import Delay, Pulse, PulseSequence, PulseType, VirtualZ
+from qibolab.pulses import Pulse, PulseSequence, PulseType
 from qibolab.pulses.pulse import PulseLike
 from qibolab.qubits import Qubit, QubitPair