diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index ae625610389..1d51c777026 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -3931,6 +3931,23 @@ void Item_func_conv::fix_length_and_dec()
 {
   collation.set(default_charset());
   max_length=64;
+  switch(collation.collation->number)
+  {
+					case 33:
+         {
+               max_length *=3;
+               break;
+         }
+         case 45:
+         {
+               max_length *=4;
+               break;
+         }
+         default:
+         {
+               //nothing
+         }
+  }
   maybe_null= 1;
   reject_geometry_args(arg_count, args, this);
 }