diff --git a/ext/io/wait/wait.c b/ext/io/wait/wait.c
index f7a7508eeb..d846bba49e 100644
--- a/ext/io/wait/wait.c
+++ b/ext/io/wait/wait.c
@@ -95,10 +95,9 @@ io_nread(VALUE io)
 
 /*
  * call-seq:
- *   io.ready? -> true, false or nil
+ *   io.ready? -> true or false
  *
  * Returns true if input available without blocking, or false.
- * Returns nil if no information available.
  */
 
 static VALUE