diff --git a/ChemistryLib/PhreeqcIO.h b/ChemistryLib/PhreeqcIO.h
index 10e431d4bac321f953b642c459d5749a353ab01d..62d80eb31722707029d17d999bb007d36f2ea97c 100644
--- a/ChemistryLib/PhreeqcIO.h
+++ b/ChemistryLib/PhreeqcIO.h
@@ -80,6 +80,6 @@ private:
     std::unique_ptr<Output> const _output;
     std::vector<std::pair<int, std::string>> const&
         _process_id_to_component_name_map;
-    double _dt;
+    double _dt = std::numeric_limits<double>::quiet_NaN();
 };
 }  // namespace ChemistryLib
diff --git a/ChemistryLib/PhreeqcIOData/AqueousSolution.h b/ChemistryLib/PhreeqcIOData/AqueousSolution.h
index 648bbc6972e08e72a38d5569754f17c262ac412d..403be34c2d0f19efcd0b5fa490cb06938c6b7076 100644
--- a/ChemistryLib/PhreeqcIOData/AqueousSolution.h
+++ b/ChemistryLib/PhreeqcIOData/AqueousSolution.h
@@ -22,7 +22,7 @@ struct Component
     explicit Component(std::string name_) : name(std::move(name_)) {}
 
     std::string const name;
-    double amount;
+    double amount = std::numeric_limits<double>::quiet_NaN();
     static const ItemType item_type = ItemType::Component;
 };
 
@@ -53,7 +53,7 @@ struct AqueousSolution
 
     double temperature;
     double pressure;
-    double pH;
+    double pH = std::numeric_limits<double>::quiet_NaN();
     double pe;
     std::vector<Component> components;
     MeansOfAdjustingCharge const means_of_adjusting_charge;