diff --git a/gtsam/hybrid/HybridGaussianProductFactor.h b/gtsam/hybrid/HybridGaussianProductFactor.h
index c94a04a2a..17d9238dd 100644
--- a/gtsam/hybrid/HybridGaussianProductFactor.h
+++ b/gtsam/hybrid/HybridGaussianProductFactor.h
@@ -57,7 +57,7 @@ class GTSAM_EXPORT HybridGaussianProductFactor
 
   /// Deleted constructor since we don't have istream operator for
   /// GaussianFactorGraphValuePair
-  HybridGaussianProductFactor(const std::vector<Key>& labelCs,
+  HybridGaussianProductFactor(const std::vector<DiscreteKey>& labelCs,
                               const std::string& table) = delete;
 
   ///@}