diff --git a/std/stdio.d b/std/stdio.d
index b4744600cd5..b6890818c3b 100644
--- a/std/stdio.d
+++ b/std/stdio.d
@@ -4607,7 +4607,7 @@ struct lines
     f = File to read lines from.
     terminator = Line separator (`'\n'` by default).
     */
-    this(File f, dchar terminator = '\n')
+    this(File f, dchar terminator = '\n') @safe nothrow @nogc pure
     {
         this.f = f;
         this.terminator = terminator;