diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index 874a3a1..986b644 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -454,7 +454,7 @@ strio_self(VALUE self)
 }
 
 /*
- * Returns 0.  Just for compatibility to IO.
+ * Returns 0; for compatibility with IO.
  */
 static VALUE
 strio_0(VALUE self)