diff --git a/radiant/preferences.cpp b/radiant/preferences.cpp
index 31bef256..8ec4126f 100644
--- a/radiant/preferences.cpp
+++ b/radiant/preferences.cpp
@@ -176,15 +176,10 @@ bool Preferences_Save( PreferenceDictionary& preferences, const char* filename )
 }
 
 bool Preferences_Save_Safe( PreferenceDictionary& preferences, const char* filename ){
-	Array<char> tmpName( filename, filename + strlen( filename ) + 1 + 3 );
-	*( tmpName.end() - 4 ) = 'T';
-	*( tmpName.end() - 3 ) = 'M';
-	*( tmpName.end() - 2 ) = 'P';
-	*( tmpName.end() - 1 ) = '\0';
-
-	return Preferences_Save( preferences, tmpName.data() )
+	const auto tmpName = StringOutputStream()( filename, "TMP" );
+	return Preferences_Save( preferences, tmpName )
 	       && ( !file_exists( filename ) || file_remove( filename ) )
-	       && file_move( tmpName.data(), filename );
+	       && file_move( tmpName, filename );
 }