diff --git a/ChemistryLib/PhreeqcIO.h b/ChemistryLib/PhreeqcIO.h
index fd60282ab42112dc60dc46a4b71813e705aadd6e..cac0fc918dde6a0ac97e0b894cbf30f132d1e893 100644
--- a/ChemistryLib/PhreeqcIO.h
+++ b/ChemistryLib/PhreeqcIO.h
@@ -81,7 +81,7 @@ public:
     std::string const _phreeqc_input_file;
 
 private:
-    void writeInputsToFile(double const dt = 0);
+    void writeInputsToFile(double const dt);
 
     void execute();