diff --git a/lua/cmp/source.lua b/lua/cmp/source.lua
index 9f13789..476cc94 100644
--- a/lua/cmp/source.lua
+++ b/lua/cmp/source.lua
@@ -195,7 +195,7 @@ source.get_trigger_characters = function(self)
 
   local trigger_characters = {}
   if self.source.get_trigger_characters then
-    trigger_characters = self.source:get_trigger_characters(misc.readonly(self:get_config())) or {}
+    trigger_characters = self.source:get_trigger_characters(misc.copy(c)) or {}
   end
   if config.get().completion.get_trigger_characters then
     return config.get().completion.get_trigger_characters(trigger_characters)
@@ -211,7 +211,7 @@ source.get_keyword_pattern = function(self)
     return c.keyword_pattern
   end
   if self.source.get_keyword_pattern then
-    return self.source:get_keyword_pattern(misc.readonly(c))
+    return self.source:get_keyword_pattern(misc.copy(c))
   end
   return config.get().completion.keyword_pattern
 end
diff --git a/lua/cmp/utils/misc.lua b/lua/cmp/utils/misc.lua
index f4ab5cf..a70d0b1 100644
--- a/lua/cmp/utils/misc.lua
+++ b/lua/cmp/utils/misc.lua
@@ -168,19 +168,6 @@ misc.to_vimindex = function(text, utfindex)
   return utfindex + 1
 end
 
----Return readonly version object
----@generic T
----@param tbl T
----@return T
-misc.readonly = function(tbl)
-  return setmetatable({}, {
-    __index = tbl,
-    __newindex = function()
-      error('this table is readonly.')
-    end,
-  })
-end
-
 ---Mark the function as deprecated
 misc.deprecated = function(fn, msg)
   local printed = false
diff --git a/lua/cmp/utils/misc_spec.lua b/lua/cmp/utils/misc_spec.lua
index cd1a35b..1cafe29 100644
--- a/lua/cmp/utils/misc_spec.lua
+++ b/lua/cmp/utils/misc_spec.lua
@@ -49,12 +49,4 @@ describe('misc', function()
     assert.are.equal(merged.a, nil)
   end)
 
-  it('readonly', function()
-    local o = { a = 1, b = 2 }
-    local r = misc.readonly(o)
-    assert.are.equal(r.a, 1)
-    assert.has_error(function()
-      r.a = 5
-    end)
-  end)
 end)