diff --git a/src/fiber.cr b/src/fiber.cr
index b34a8762037d..b27c34fd6b36 100644
--- a/src/fiber.cr
+++ b/src/fiber.cr
@@ -162,6 +162,10 @@ class Fiber
     @timeout_event.try &.free
     @timeout_select_action = nil
 
+    # Additional cleanup (avoid stale references)
+    @exec_recursive_hash = nil
+    @exec_recursive_clone_hash = nil
+
     @alive = false
     {% unless flag?(:interpreted) %}
       Crystal::Scheduler.stack_pool.release(@stack)
@@ -331,4 +335,18 @@ class Fiber
       @current_thread.lazy_get
     end
   {% end %}
+
+  # :nodoc:
+  #
+  # See `Reference#exec_recursive` for details.
+  def exec_recursive_hash
+    @exec_recursive_hash ||= Hash({UInt64, Symbol}, Nil).new
+  end
+
+  # :nodoc:
+  #
+  # See `Reference#exec_recursive_clone` for details.
+  def exec_recursive_clone_hash
+    @exec_recursive_clone_hash ||= Hash(UInt64, UInt64).new
+  end
 end
diff --git a/src/reference.cr b/src/reference.cr
index f70697282fa0..42bdcba2327a 100644
--- a/src/reference.cr
+++ b/src/reference.cr
@@ -1,7 +1,3 @@
-{% if flag?(:preview_mt) %}
-  require "crystal/thread_local_value"
-{% end %}
-
 # `Reference` is the base class of classes you define in your program.
 # It is set as a class' superclass when you don't specify one:
 #
@@ -180,28 +176,9 @@ class Reference
     io << '>'
   end
 
-  # :nodoc:
-  module ExecRecursive
-    # NOTE: can't use `Set` here because of prelude require order
-    alias Registry = Hash({UInt64, Symbol}, Nil)
-
-    {% if flag?(:preview_mt) %}
-      @@exec_recursive = Crystal::ThreadLocalValue(Registry).new
-    {% else %}
-      @@exec_recursive = Registry.new
-    {% end %}
-
-    def self.hash
-      {% if flag?(:preview_mt) %}
-        @@exec_recursive.get { Registry.new }
-      {% else %}
-        @@exec_recursive
-      {% end %}
-    end
-  end
-
   private def exec_recursive(method, &)
-    hash = ExecRecursive.hash
+    # NOTE: can't use `Set` because of prelude require order
+    hash = Fiber.current.exec_recursive_hash
     key = {object_id, method}
     hash.put(key, nil) do
       yield
@@ -211,25 +188,6 @@ class Reference
     false
   end
 
-  # :nodoc:
-  module ExecRecursiveClone
-    alias Registry = Hash(UInt64, UInt64)
-
-    {% if flag?(:preview_mt) %}
-      @@exec_recursive = Crystal::ThreadLocalValue(Registry).new
-    {% else %}
-      @@exec_recursive = Registry.new
-    {% end %}
-
-    def self.hash
-      {% if flag?(:preview_mt) %}
-        @@exec_recursive.get { Registry.new }
-      {% else %}
-        @@exec_recursive
-      {% end %}
-    end
-  end
-
   # Helper method to perform clone by also checking recursiveness.
   # When clone is wanted, call this method. Then create the clone
   # instance without any contents (don't fill it out yet), then
@@ -249,7 +207,8 @@ class Reference
   # end
   # ```
   private def exec_recursive_clone(&)
-    hash = ExecRecursiveClone.hash
+    # NOTE: can't use `Set` because of prelude require order
+    hash = Fiber.current.exec_recursive_clone_hash
     clone_object_id = hash[object_id]?
     unless clone_object_id
       clone_object_id = yield(hash).object_id