diff --git a/libmei/addons/att.cpp b/libmei/addons/att.cpp
index d99e63be16..42eb1326aa 100644
--- a/libmei/addons/att.cpp
+++ b/libmei/addons/att.cpp
@@ -23,26 +23,26 @@ namespace vrv {
 // Att
 //----------------------------------------------------------------------------
 
-std::string Att::StrToStr(std::string str) const
+std::string Att::StrToStr(const std::string &str) const
 {
     return str;
 }
 
 // Basic converters for writing
 
-std::string Att::DblToStr(double data) const
+std::string Att::DblToStr(const double data) const
 {
     std::stringstream sstream;
     sstream << round(data * 10000.0) / 10000.0;
     return sstream.str();
 }
 
-std::string Att::IntToStr(int data) const
+std::string Att::IntToStr(const int data) const
 {
     return StringFormat("%d", data);
 }
 
-std::string Att::VUToStr(data_VU data) const
+std::string Att::VUToStr(const data_VU data) const
 {
     return DblToStr(data) + "vu";
 }
diff --git a/libmei/addons/att.h b/libmei/addons/att.h
index 17f71d0aa2..b2a511457b 100644
--- a/libmei/addons/att.h
+++ b/libmei/addons/att.h
@@ -42,7 +42,7 @@ class Att : public AttConverterBase {
     static data_STAFFREL_basic StaffrelToStaffrelBasic(data_STAFFREL staffrel);
 
     /** Dummy string converter */
-    std::string StrToStr(const std::string str) const;
+    std::string StrToStr(const std::string &str) const;
 
     /** @name Basic converters for writing */
     ///@{
@@ -90,7 +90,10 @@ class Att : public AttConverterBase {
     std::string MeasurementsignedToStr(data_MEASUREMENTSIGNED data) const;
     data_MEASUREMENTSIGNED StrToMeasurementsigned(const std::string &value, bool logWarning = true) const;
 
-    inline std::string MeasurementunsignedToStr(data_MEASUREMENTUNSIGNED data) const { return MeasurementsignedToStr(data); }
+    inline std::string MeasurementunsignedToStr(data_MEASUREMENTUNSIGNED data) const
+    {
+        return MeasurementsignedToStr(data);
+    }
     inline data_MEASUREMENTUNSIGNED StrToMeasurementunsigned(const std::string &value, bool logWarning = true) const
     {
         return StrToMeasurementsigned(value, logWarning);