diff --git a/gtsam/inference/Conditional-inst.h b/gtsam/inference/Conditional-inst.h
index 30433263c..ee13946d9 100644
--- a/gtsam/inference/Conditional-inst.h
+++ b/gtsam/inference/Conditional-inst.h
@@ -54,6 +54,6 @@ double Conditional<FACTOR, DERIVEDCONDITIONAL>::logProbability(
 template <class FACTOR, class DERIVEDCONDITIONAL>
 double Conditional<FACTOR, DERIVEDCONDITIONAL>::evaluate(
     const HybridValues& c) const {
-  return exp(static_cast<const DERIVEDCONDITIONAL*>(this)->logProbability(c));
+  throw std::runtime_error("Conditional::evaluate is not implemented");
 }
 }  // namespace gtsam
diff --git a/gtsam/symbolic/SymbolicConditional.cpp b/gtsam/symbolic/SymbolicConditional.cpp
index eb8a95cff..fd9cc453d 100644
--- a/gtsam/symbolic/SymbolicConditional.cpp
+++ b/gtsam/symbolic/SymbolicConditional.cpp
@@ -15,7 +15,6 @@
  * @date    Oct 17, 2010
  */
 
-#include <gtsam/inference/Conditional-inst.h>
 #include <gtsam/symbolic/SymbolicConditional.h>
 
 namespace gtsam {
@@ -38,5 +37,10 @@ double SymbolicConditional::logProbability(const HybridValues& c) const {
   throw std::runtime_error("SymbolicConditional::logProbability is not implemented");
 }
 
+/* ************************************************************************* */
+double SymbolicConditional::evaluate(const HybridValues& c) const {
+  throw std::runtime_error("SymbolicConditional::evaluate is not implemented");
+}
+
 
 }  // namespace gtsam
diff --git a/gtsam/symbolic/SymbolicConditional.h b/gtsam/symbolic/SymbolicConditional.h
index 8970902d7..6bd966450 100644
--- a/gtsam/symbolic/SymbolicConditional.h
+++ b/gtsam/symbolic/SymbolicConditional.h
@@ -17,10 +17,10 @@
 
 #pragma once
 
-#include <gtsam/symbolic/SymbolicFactor.h>
-#include <gtsam/inference/Conditional.h>
 #include <gtsam/base/Testable.h>
 #include <gtsam/base/types.h>
+#include <gtsam/inference/Conditional-inst.h>
+#include <gtsam/symbolic/SymbolicFactor.h>
 
 namespace gtsam {
 
@@ -114,12 +114,12 @@ namespace gtsam {
     /// @name HybridValues methods.
     /// @{
 
-    /**
-     * logProbability throws exception, symbolic.
-     */
+    /// logProbability throws exception, symbolic.
     double logProbability(const HybridValues& x) const override;
 
-    using Conditional::evaluate; // Expose evaluate(const HybridValues&) method..
+    /// evaluate throws exception, symbolic.
+    double evaluate(const HybridValues& x) const override;
+
     using Conditional::operator(); // Expose evaluate(const HybridValues&) method..
     using SymbolicFactor::error; // Expose error(const HybridValues&) method..