diff --git a/gtsam/discrete/DiscreteLookupDAG.cpp b/gtsam/discrete/DiscreteLookupDAG.cpp
index 37e45de80..4fe3a53a4 100644
--- a/gtsam/discrete/DiscreteLookupDAG.cpp
+++ b/gtsam/discrete/DiscreteLookupDAG.cpp
@@ -27,10 +27,6 @@ using std::vector;
 
 namespace gtsam {
 
-// Instantiate base class
-template class GTSAM_EXPORT
-    Conditional<DecisionTreeFactor, DiscreteLookupTable>;
-
 /* ************************************************************************** */
 // TODO(dellaert): copy/paste from DiscreteConditional.cpp :-(
 void DiscreteLookupTable::print(const std::string& s,
diff --git a/gtsam/discrete/DiscreteLookupDAG.h b/gtsam/discrete/DiscreteLookupDAG.h
index a69b0b1ee..31cb3dfbf 100644
--- a/gtsam/discrete/DiscreteLookupDAG.h
+++ b/gtsam/discrete/DiscreteLookupDAG.h
@@ -22,17 +22,19 @@
 #include <gtsam/inference/FactorGraph.h>
 
 #include <boost/shared_ptr.hpp>
-
+#include <string>
+#include <utility>
 #include <vector>
 
 namespace gtsam {
 
 /**
  * @brief DiscreteLookupTable table for max-product
+ *
+ * Inherits from discrete conditional for convenience, but is not normalized.
+ * Is used in pax-product algorithm.
  */
-class DiscreteLookupTable
-    : public DecisionTreeFactor,
-      public Conditional<DecisionTreeFactor, DiscreteLookupTable> {
+class DiscreteLookupTable : public DiscreteConditional {
  public:
   using This = DiscreteLookupTable;
   using shared_ptr = boost::shared_ptr<This>;
@@ -47,7 +49,7 @@ class DiscreteLookupTable
    */
   DiscreteLookupTable(size_t nFrontals, const DiscreteKeys& keys,
                       const ADT& potentials)
-      : DecisionTreeFactor(keys, potentials), BaseConditional(nFrontals) {}
+      : DiscreteConditional(nFrontals, keys, potentials) {}
 
   /// GTSAM-style print
   void print(
@@ -100,6 +102,12 @@ class GTSAM_EXPORT DiscreteLookupDAG : public BayesNet<DiscreteLookupTable> {
   /// @name Standard Interface
   /// @{
 
+  /** Add a DiscreteLookupTable */
+  template <typename... Args>
+  void add(Args&&... args) {
+    emplace_shared<DiscreteLookupTable>(std::forward<Args>(args)...);
+  }
+
   /**
    * @brief argmax by back-substitution.
    *
diff --git a/gtsam/discrete/tests/testDiscreteFactorGraph.cpp b/gtsam/discrete/tests/testDiscreteFactorGraph.cpp
index e63cc26b8..f4819dab5 100644
--- a/gtsam/discrete/tests/testDiscreteFactorGraph.cpp
+++ b/gtsam/discrete/tests/testDiscreteFactorGraph.cpp
@@ -239,7 +239,7 @@ TEST(DiscreteFactorGraph, testMPE_Darwiche09book_p244) {
   Ordering ordering;
   ordering += Key(0), Key(1), Key(2), Key(3), Key(4);
   auto chordal = graph.eliminateSequential(ordering);
-  EXPECT_LONGS_EQUAL(2, chordal->size());
+  EXPECT_LONGS_EQUAL(5, chordal->size());
 #ifdef GTSAM_ALLOW_DEPRECATED_SINCE_V42
   auto notOptimal = chordal->optimize();  // not MPE !
   EXPECT(graph(notOptimal) < graph(mpe));
diff --git a/gtsam/discrete/tests/testDiscreteLookupDAG.cpp b/gtsam/discrete/tests/testDiscreteLookupDAG.cpp
new file mode 100644
index 000000000..04b859780
--- /dev/null
+++ b/gtsam/discrete/tests/testDiscreteLookupDAG.cpp
@@ -0,0 +1,58 @@
+/* ----------------------------------------------------------------------------
+
+ * GTSAM Copyright 2010, Georgia Tech Research Corporation,
+ * Atlanta, Georgia 30332-0415
+ * All Rights Reserved
+ * Authors: Frank Dellaert, et al. (see THANKS for the full author list)
+
+ * See LICENSE for the license information
+
+ * -------------------------------------------------------------------------- */
+
+/*
+ * testDiscreteLookupDAG.cpp
+ *
+ *  @date January, 2022
+ *  @author Frank Dellaert
+ */
+
+#include <CppUnitLite/TestHarness.h>
+#include <gtsam/base/Testable.h>
+#include <gtsam/discrete/DiscreteLookupDAG.h>
+
+#include <boost/assign/list_inserter.hpp>
+#include <boost/assign/std/map.hpp>
+
+using namespace gtsam;
+using namespace boost::assign;
+
+/* ************************************************************************* */
+TEST(DiscreteLookupDAG, argmax) {
+  using ADT = AlgebraicDecisionTree<Key>;
+
+  // Declare 2 keys
+  DiscreteKey A(0, 2), B(1, 2);
+
+  // Create lookup table corresponding to "marginalIsNotMPE" in testDFG.
+  DiscreteLookupDAG dag;
+
+  ADT adtB(DiscreteKeys{B, A}, std::vector<double>{0.5, 1. / 3, 0.5, 2. / 3});
+  dag.add(1, DiscreteKeys{B, A}, adtB);
+
+  ADT adtA(A, 0.5 * 10 / 19, (2. / 3) * (9. / 19));
+  dag.add(1, DiscreteKeys{A}, adtA);
+
+  // The expected MPE is A=1, B=1
+  DiscreteValues mpe;
+  insert(mpe)(0, 1)(1, 1);
+
+  // check:
+  auto actualMPE = dag.argmax();
+  EXPECT(assert_equal(mpe, actualMPE));
+}
+/* ************************************************************************* */
+int main() {
+  TestResult tr;
+  return TestRegistry::runAllTests(tr);
+}
+/* ************************************************************************* */