diff --git a/stl/boolean_eval.py b/stl/boolean_eval.py
index e1884fc..ba12b4d 100644
--- a/stl/boolean_eval.py
+++ b/stl/boolean_eval.py
@@ -26,28 +26,34 @@ def _(stl):
     return lambda x, t: all(f(x, t) for f in fs)
 
 
+def get_times(x, tau, lo=None, hi=None):
+    indices = x.index if lo is None or hi is None else x[lo:hi].index
+    return [min(tau + t2, x.index[-1]) for t2 in indices]
+
+
 @pointwise_sat.register(stl.Until)
 def _(stl):
     def _until(x, t):
-        phi = (pointwise_sat(phi)(x, t) for t in x.index)
-    return lambda x, t: any((pointwise_sat(stl.arg)(x, min(t + t2, x.index[-1]))
-                             for t2 in x[lo:hi].index))
+        f1, f2 = pointwise_sat(stl.arg1), pointwise_sat(stl.arg2)
+        for tau in get_times(x, t):
+            if not f1(x, tau):
+                return f2(x, tau)
+        return False
+    return _until
 
 
 @pointwise_sat.register(stl.F)
 def _(stl):
     lo, hi = stl.interval
     f = pointwise_sat(stl.arg) 
-    return lambda x, t: any((f(x, min(t + t2, x.index[-1]))
-                             for t2 in x[lo:hi].index))
+    return lambda x, t: any(f(x, tau) for tau in get_times(x, t, lo, hi))
 
 
 @pointwise_sat.register(stl.G)
 def _(stl):
     lo, hi = stl.interval
-    f = pointwise_sat(stl.arg) 
-    return lambda x, t: all((pointwise_sat(stl.arg)(x, min(t + t2, x.index[-1])) 
-                             for t2 in x[lo:hi].index))
+    f = pointwise_sat(stl.arg)
+    return lambda x, t: all(f(x, tau) for tau in get_times(x, t, lo, hi))
 
 
 @pointwise_sat.register(stl.Neg)
diff --git a/stl/fastboolean_eval.py b/stl/fastboolean_eval.py
index 9cbb7be..b2cec06 100644
--- a/stl/fastboolean_eval.py
+++ b/stl/fastboolean_eval.py
@@ -4,7 +4,7 @@ from operator import and_, or_
 from bitarray import bitarray
 
 import stl.ast
-from stl.boolean_eval import eval_terms, op_lookup
+from stl.boolean_eval import eval_terms, op_lookup, get_times
 
 def pointwise_sat(stl):
     f = pointwise_satf(stl)
@@ -30,15 +30,11 @@ def _(stl):
     return bool_op(stl, conjunction=True)
 
 
-def get_times(x, lo, hi, tau):
-    return [min(tau + t2, x.index[-1]) for t2 in x[lo:hi].index]
-
-
 def temporal_op(stl, lo, hi, conjunction=False):
     fold = bitarray.all if conjunction else bitarray.any
     f = pointwise_satf(stl.arg)
     def sat_comp(x,t):
-        return bitarray(fold(f(x, get_times(x, lo, hi, tau))) for tau in t)
+        return bitarray(fold(f(x, get_times(x, tau, lo, hi))) for tau in t)
     return sat_comp
 
 
diff --git a/stl/test_boolean_eval.py b/stl/test_boolean_eval.py
index d0bb532..25fab18 100644
--- a/stl/test_boolean_eval.py
+++ b/stl/test_boolean_eval.py
@@ -15,11 +15,13 @@ ex6 = ("G[0, 0.1](A < 0)", False)
 ex7 = ("G[0, 0.1](C)", True)
 ex8 = ("G[0, 0.2](C)", False)
 ex9 = ("(F[0, 0.2](C)) and (F[0, 1](2*A > 3))", True)
+ex10 = ("(A = 1) U (A = 4)", True)
+ex11 = ("(A < 5) U (A = 4)", False)
 x = pd.DataFrame([[1,2, True], [1,4, True], [4,2, False]], index=[0,0.1,0.2], 
                  columns=["A", "B", "C"])
 
 class TestSTLEval(unittest.TestCase):
-    @params(ex1, ex2, ex3, ex4, ex5, ex6, ex7, ex8, ex9)
+    @params(ex1, ex2, ex3, ex4, ex5, ex6, ex7, ex8, ex9, ex10, ex11)
     def test_eval(self, phi_str, r):
         phi = stl.parse(phi_str)
         stl_eval = stl.boolean_eval.pointwise_sat(phi)