diff --git a/lib/cztop/async.rb b/lib/cztop/async.rb
index 1138a00..bed428a 100644
--- a/lib/cztop/async.rb
+++ b/lib/cztop/async.rb
@@ -49,6 +49,8 @@ def <<(...)
       def wait_readable(timeout = read_timeout)
         @io_fd ||= ::IO.for_fd @io.fd, autoclose: false
 
+        return true if @io.readable?
+
         if timeout
           timeout_at = now + timeout
 
@@ -67,6 +69,8 @@ def wait_readable(timeout = read_timeout)
       def wait_writable(timeout = write_timeout)
         @io_fd ||= ::IO.for_fd @io.fd, autoclose: false
 
+        return true if @io.writable?
+
         if timeout
           timeout_at = now + timeout