diff --git a/base/io.jl b/base/io.jl
index 0f13e59baea8d..36e0a1f9949ec 100644
--- a/base/io.jl
+++ b/base/io.jl
@@ -31,7 +31,9 @@ struct SystemError <: Exception
 end
 
 lock(::IO) = nothing
+typeof(lock).name.max_methods = UInt8(1)
 unlock(::IO) = nothing
+typeof(unlock).name.max_methods = UInt8(1)
 
 """
     reseteof(io)