diff --git a/base/task.jl b/base/task.jl
index 5a1b37d4252a8..db2f7e22bce67 100644
--- a/base/task.jl
+++ b/base/task.jl
@@ -691,7 +691,7 @@ end
 
 ## scheduler and work queue
 
-struct IntrusiveLinkedListSynchronized{T}
+mutable struct IntrusiveLinkedListSynchronized{T}
     queue::IntrusiveLinkedList{T}
     lock::Threads.SpinLock
     IntrusiveLinkedListSynchronized{T}() where {T} = new(IntrusiveLinkedList{T}(), Threads.SpinLock())