diff --git a/src/g_level.cpp b/src/g_level.cpp
index aa6fb013d..e480d11a8 100644
--- a/src/g_level.cpp
+++ b/src/g_level.cpp
@@ -1730,8 +1730,7 @@ FString CalcMapName (int episode, int level)
 	}
 	else
 	{
-		lumpname = "";
-		lumpname << 'E' << ('0' + episode) << 'M' << ('0' + level);
+		lumpname.Format("E%01dM%01d", episode, level);
 	}
 	return lumpname;
 }