diff --git a/lib/net/protocol.rb b/lib/net/protocol.rb
index 7e42d22..7876fb4 100644
--- a/lib/net/protocol.rb
+++ b/lib/net/protocol.rb
@@ -384,6 +384,9 @@ def write0(*strs)
             # next string
           end
           # continue looping
+        when :wait_readable
+          (io = @io.to_io).wait_readable(@write_timeout) or raise Net::WriteTimeout.new(io)
+          # continue looping
         when :wait_writable
           (io = @io.to_io).wait_writable(@write_timeout) or raise Net::WriteTimeout.new(io)
           # continue looping