diff --git a/src/spe.py b/src/spe.py
index f68fbd2..bde14f7 100644
--- a/src/spe.py
+++ b/src/spe.py
@@ -51,7 +51,7 @@ def memoize(f):
     def f_(*args):
         (spe, event_factor, memo) = args
         if memo is False:
-            return f(spe, event_factor_to_event, memo)
+            return f(spe, event_factor, memo)
         m = getattr(memo, table)
         key = spe.get_memo_key(event_factor)
         if key not in m:
diff --git a/tests/test_product.py b/tests/test_product.py
index 0e30e72..afd6319 100644
--- a/tests/test_product.py
+++ b/tests/test_product.py
@@ -73,7 +73,7 @@ def test_product_inclusion_exclusion_basic():
     Y = Id('Y')
     spe = ProductSPE([X << norm(loc=0, scale=1), Y << gamma(a=1)])
 
-    a = spe.logprob(X > 0.1)
+    a = spe.logprob(X > 0.1, memo=False)
     b = spe.logprob(Y < 0.5)
     c = spe.logprob((X > 0.1) & (Y < 0.5))
     d = spe.logprob((X > 0.1) | (Y < 0.5))
@@ -120,7 +120,7 @@ def test_product_condition_basic():
     # where the second clause reduces to first as Y < 0
     # has probability zero.
     for event in [(X > 0), (X  > 0) | (Y < 0)]:
-        dX = spe.condition(event)
+        dX = spe.condition(event, memo=False)
         assert isinstance(dX, ProductSPE)
         assert dX.children[0].symbol == Id('X')
         assert dX.children[0].conditioned