diff --git a/src/science_signal/signal.py b/src/science_signal/signal.py
index efe28e4..f66a487 100644
--- a/src/science_signal/signal.py
+++ b/src/science_signal/signal.py
@@ -6,6 +6,7 @@ from numpy import (
     float64,
     linspace,
     array,
+    logical_and,
     logical_or,
     sin,
     where,