diff --git a/app/otbHarmonizer.cxx b/app/otbHarmonizer.cxx
index a8b3390a508e5df0bf20ba4f86c783c153bd80e9..79d9c4e749c68c62612db6456ed027012fd088ff 100644
--- a/app/otbHarmonizer.cxx
+++ b/app/otbHarmonizer.cxx
@@ -300,6 +300,14 @@ private:
     AddChoice("zeroy.on", "Yes (y=ax)");
     AddChoice("zeroy.off", "No (y=ax+b)");
 
+    AddParameter(ParameterType_StringList, "outgains", "output gains");
+    SetParameterRole("outgains", Role_Output);
+    EnableParameter("outgains");
+    AddParameter(ParameterType_StringList, "outoffsets", "output offsets");
+    SetParameterRole("outoffsets", Role_Output);
+    EnableParameter("outoffsets");
+
+
     AddRAMParameter();
 
     // Doc example parameter settings
@@ -444,11 +452,11 @@ private:
 
       if (band>0)
         exp << ";";
-      exp << "im1b" << (band+1) << "*" << b1;
+      exp << "im1b" << (band+1) << "*" << std::to_string(b1);
       if (b0>0)
-        exp << "+" << b0;
+        exp << "+" << std::to_string(b0);
       else
-        exp << "" << b0;
+        exp << "" << std::to_string(b0);
 
       gain[band] = b1;
       offset[band] = b0;