diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc34c198..df3a2563 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## 3.6.0
 
+* [#871](https://github.com/CanCanCommunity/cancancan/pull/871): Make `with_accessible_by_strategy` thread safe ([@NikosVlagoidis][])
 * [#849](https://github.com/CanCanCommunity/cancancan/pull/849): Update tests matrix. ([@coorasse][])
 * [#843](https://github.com/CanCanCommunity/cancancan/pull/843): Compress duplicate rules. ([@MrChoclate][])
 * [#841](https://github.com/CanCanCommunity/cancancan/pull/841): New https://cancancan.dev website. ([@pandermatt][])
@@ -716,3 +717,4 @@ Please read the [guide on migrating from CanCanCan 2.x to 3.0](https://github.co
 [@MrChoclate]: https://github.com/MrChoclate
 [@pandermatt]: https://github.com/pandermatt
 [@kalsan]: https://github.com/kalsan
+[@NikosVlagoidis]: https://github.com/NikosVlagoidis
diff --git a/lib/cancan/config.rb b/lib/cancan/config.rb
index 0fd8893f..f192cf44 100644
--- a/lib/cancan/config.rb
+++ b/lib/cancan/config.rb
@@ -48,9 +48,7 @@ def self.with_rules_compressor_enabled(value)
   #                `distinct` is not reliable in some cases. See
   #                https://github.com/CanCanCommunity/cancancan/pull/605
   def self.accessible_by_strategy
-    return @accessible_by_strategy if @accessible_by_strategy
-
-    @accessible_by_strategy = default_accessible_by_strategy
+    Thread.current[:can_can_accessible_by_strategy] ||= default_accessible_by_strategy
   end
 
   def self.default_accessible_by_strategy
@@ -71,20 +69,18 @@ def self.accessible_by_strategy=(value)
       raise ArgumentError, 'accessible_by_strategy = :subquery requires ActiveRecord 5 or newer'
     end
 
-    @accessible_by_strategy = value
+    Thread.current[:can_can_accessible_by_strategy] = value
   end
 
   def self.with_accessible_by_strategy(value)
     return yield if value == accessible_by_strategy
 
-    validate_accessible_by_strategy!(value)
-
     begin
       strategy_was = accessible_by_strategy
-      @accessible_by_strategy = value
+      self.accessible_by_strategy = value
       yield
     ensure
-      @accessible_by_strategy = strategy_was
+      self.accessible_by_strategy = strategy_was
     end
   end