diff --git a/gtsam/discrete/TableFactor.cpp b/gtsam/discrete/TableFactor.cpp
index 63e9e5d6b4..3cfae56eca 100644
--- a/gtsam/discrete/TableFactor.cpp
+++ b/gtsam/discrete/TableFactor.cpp
@@ -260,7 +260,7 @@ DecisionTreeFactor TableFactor::toDecisionTreeFactor() const {
       ss << keyValueForIndex(key, i);
     }
     // k will be in reverse key order already
-    uint64_t k = std::strtoull(ss.str().c_str(), NULL, 10);
+    uint64_t k = std::stoll(ss.str().c_str());
     pair_table.push_back(std::make_pair(k, sparse_table_.coeff(i)));
   }