diff --git a/tools/sdbusplus/templates/interface.mako.server.cpp.in b/tools/sdbusplus/templates/interface.mako.server.cpp.in
index 165db62..821f42a 100644
--- a/tools/sdbusplus/templates/interface.mako.server.cpp.in
+++ b/tools/sdbusplus/templates/interface.mako.server.cpp.in
@@ -190,7 +190,7 @@
 
 } // anonymous namespace
 
-auto ${classname}::convert${e.name}FromString(std::string& s) ->
+auto ${classname}::convert${e.name}FromString(const std::string& s) ->
         ${e.name}
 {
     auto i = std::find_if(
diff --git a/tools/sdbusplus/templates/interface.mako.server.hpp b/tools/sdbusplus/templates/interface.mako.server.hpp
index c67f9b7..7015ca0 100644
--- a/tools/sdbusplus/templates/interface.mako.server.hpp
+++ b/tools/sdbusplus/templates/interface.mako.server.hpp
@@ -105,7 +105,7 @@
      *                 "${interface.name}.<value name>"
      *  @return - The enum value.
      */
-    static ${e.name} convert${e.name}FromString(std::string& s);
+    static ${e.name} convert${e.name}FromString(const std::string& s);
     % endfor
 
     private: