diff --git a/stl/boolean_eval.py b/stl/boolean_eval.py
index 9fdf6ec..7c63eed 100644
--- a/stl/boolean_eval.py
+++ b/stl/boolean_eval.py
@@ -33,8 +33,10 @@ def get_times(x, tau, lo=None, hi=None):
         lo = min(v.first()[0] for v in x.values())
     if hi is None or hi is oo:
         hi = max(v.last()[0] for v in x.values())
-    lo += tau
-    hi += tau
+    end = min(v.domain.end() for v in x.values())
+    hi = hi + tau if hi + tau <= end else end
+    lo = lo + tau if lo + tau <= end else end
+
     if lo > hi:
         return []
     elif hi == lo: