diff --git a/classwrapper.h b/classwrapper.h
index d341c7f..a236eb8 100644
--- a/classwrapper.h
+++ b/classwrapper.h
@@ -78,7 +78,7 @@ namespace upywrap
       ClassWrapper( name, flags )
     {
       mp_obj_dict_store( dict, new_qstr( name ), &type );
-      mp_obj_dict_store( dict, new_qstr( ( std::string( name ) + "_locals" ).data() ), MP_OBJ_FROM_PTR( MP_OBJ_TYPE_GET_SLOT( &type, locals_dict ) ) );
+      mp_obj_dict_store( dict, new_qstr_from_concat_str( name, "_locals" ), MP_OBJ_FROM_PTR( MP_OBJ_TYPE_GET_SLOT( &type, locals_dict ) ) );
     }
 
     //Initialize the type, storing the locals in StaticPyObjectStore to prevent GC collection.
@@ -647,11 +647,10 @@ namespace upywrap
       if( type.base.type == nullptr )
       {
 #if UPYWRAP_HAS_TYPEID
-        std::string errorMessage( std::string( "Native type " ) + typeid( T ).name() + " has not been registered" );
+        RaiseTypeExceptionFmt( "Native type %s has not been registered", typeid( T ).name() );
 #else
-        std::string errorMessage( "Native type has not been registered" );
+        RaiseTypeException( "Native type has not been registered" );
 #endif
-        RaiseTypeException( errorMessage.c_str() );
       }
     }
 
@@ -674,7 +673,7 @@ namespace upywrap
       callerObject->arguments = std::move( arguments );
       functionPointers[ (void*) name ] = callerObject;
       AddFunctionToTable( name(), call_type::CreateUPyFunction( *callerObject ) );
-      if( std::string( name() ) == "__call__" )
+      if( std::string_view( name() ) == "__call__" )
       {
         MP_OBJ_TYPE_SET_SLOT( &type, call, instance_call, 5 );
       }
@@ -824,7 +823,7 @@ namespace upywrap
         {
           if( caller.arguments.NumberOfArguments() != sizeof...( A ) )
           {
-            RaiseTypeException( ( std::string( "Wrong number of arguments in definition of " ) + index() ).data() );
+            RaiseTypeExceptionFmt(  "Wrong number of arguments in definition of %s", index() );
           }
           return MakeFunction( caller.arguments.MimimumNumberOfArguments(), CallKw );
         }
@@ -847,7 +846,7 @@ namespace upywrap
         {
           if( f->arguments.NumberOfArguments() != sizeof...( A ) )
           {
-            RaiseTypeException( ( std::string( "Wrong number of arguments in definition of " ) + index() ).data() );
+            RaiseTypeExceptionFmt(  "Wrong number of arguments in definition of %s", index() );
           }
           Arguments::parsed_obj_t parsedArgs{};
           f->arguments.Parse( n_args, n_kw, args, parsedArgs );
@@ -857,7 +856,7 @@ namespace upywrap
         }
         else if( n_args != sizeof...( A ) || n_kw )
         {
-          RaiseTypeException( ( std::string( "Wrong number of arguments in definition of " ) + index() ).data() );
+          RaiseTypeExceptionFmt(  "Wrong number of arguments in definition of %s", index() );
         }
         UPYWRAP_TRY
         return AsPyObj( native_obj_t( Apply( f, args, make_index_sequence< sizeof...( A ) >() ) ) );
diff --git a/detail/micropython.h b/detail/micropython.h
index 73f87f4..3a9f70b 100644
--- a/detail/micropython.h
+++ b/detail/micropython.h
@@ -3,6 +3,7 @@
 
 #include "micropythonc.h"
 #include <cmath>
+#include <cstdarg>
 #include <cstdint>
 #include <cstring>
 #include <limits>
@@ -21,6 +22,17 @@ namespace upywrap
     return new_qstr( qstr_from_str( what ) );
   }
 
+  inline mp_obj_t new_qstr_from_concat_str( const char* str1, const char* str2 )
+  {
+      vstr_t concat_str {};
+      vstr_init_len( &concat_str, strlen( str1 ) + strlen( str2 ) );
+      vstr_add_str( &concat_str, str1 );
+      vstr_add_str( &concat_str, str2 );
+      mp_obj_t concat_qstr = new_qstr(qstr_from_str( concat_str.buf ));
+      vstr_clear( &concat_str );
+      return concat_qstr;
+  }
+
   inline mp_obj_t MakeFunction( mp_obj_t (*fun) ( void ) )
   {
     auto o = mp_obj_malloc( mp_obj_fun_builtin_fixed_t, &mp_type_fun_builtin_0 );
@@ -110,15 +122,17 @@ namespace upywrap
     * Use in place of mp_obj_new_exception_msg if the message string needs to be copied
     * (mp_obj_new_exception_msg assumes the message passed to it is in ROM so just stores the char pointer)
     */
-  inline mp_obj_t RaiseException( const mp_obj_type_t* exc_type, const char* msg )
+  inline mp_obj_t RaiseException( const mp_obj_type_t* exc_type, const char* fmt, ... )
   {
-    mp_obj_exception_t* o = mp_obj_malloc_var( mp_obj_exception_t, args, mp_obj_tuple_t, 0, exc_type );
-    o->traceback_data = nullptr;
-    o->args = reinterpret_cast< mp_obj_tuple_t* >( MP_OBJ_TO_PTR( mp_obj_new_tuple( 1, nullptr ) ) );
-    o->args->items[ 0 ] = mp_obj_new_str( msg, std::strlen( msg ) );
-    nlr_raise( MP_OBJ_FROM_PTR( o ) );
+    va_list args;
+    va_start(args, fmt);
+    mp_obj_t exc = mp_obj_new_exception_msg_varg(exc_type, MP_ERROR_TEXT ( fmt ), args);
+    va_end(args);
+    nlr_raise( exc );
   }
 
+#define RaiseTypeExceptionFmt( msg, ... ) RaiseException( &mp_type_TypeError, msg, ##__VA_ARGS__ )
+
   inline void RaiseTypeException( const char* msg )
   {
     RaiseException( &mp_type_TypeError, msg );
diff --git a/detail/micropythonc.h b/detail/micropythonc.h
index c04347b..4bade63 100644
--- a/detail/micropythonc.h
+++ b/detail/micropythonc.h
@@ -22,4 +22,4 @@ extern "C"
 #pragma warning ( default : 4200 )
 #endif
 
-#endif //#ifndef MICROPYTHON_WRAP_DETAIL_MICROPYTHONC_H
+#endif //#ifndef MICROPYTHON_WRAP_DETAIL_MICROPYTHONC_H
\ No newline at end of file
diff --git a/functionwrapper.h b/functionwrapper.h
index aef79d1..7dbe5ac 100644
--- a/functionwrapper.h
+++ b/functionwrapper.h
@@ -80,7 +80,7 @@ namespace upywrap
         {
           if( caller.arguments.NumberOfArguments() != sizeof...( A ) )
           {
-            RaiseTypeException( ( std::string( "Wrong number of arguments in definition of " ) + index() ).data()  );
+            RaiseTypeExceptionFmt( "Wrong number of arguments in definition of %s", index() );
           }
           return MakeFunction( caller.arguments.MimimumNumberOfArguments(), CallKw );
         }