diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 7f26ebf92bb6157a2f2a8264e1fc389ffb3c1ca8..08adbd6bb73752010999d8899386f583a4e7eb9e 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,36 @@
+*   Make ActiveSupport::Logger Fiber-safe. Fixes #36752.
+
+    Use `Fiber.current.__id__` in `ActiveSupport::Logger#local_level=` in order
+    to make log level local to Ruby Fibers in addition to Threads.
+
+    Example:
+
+        logger = ActiveSupport::Logger.new(STDOUT)
+        logger.level = 1
+        p "Main is debug? #{logger.debug?}"
+
+        Fiber.new {
+          logger.local_level = 0
+          p "Thread is debug? #{logger.debug?}"
+        }.resume
+
+        p "Main is debug? #{logger.debug?}"
+
+    Before:
+
+        Main is debug? false
+        Thread is debug? true
+        Main is debug? true
+
+    After:
+
+        Main is debug? false
+        Thread is debug? true
+        Main is debug? false
+
+    *Alexander Varnin*
+
+
 ## Rails 5.2.3 (March 27, 2019) ##
 
 *   Add `ActiveSupport::HashWithIndifferentAccess#assoc`.
diff --git a/activesupport/lib/active_support/logger_thread_safe_level.rb b/activesupport/lib/active_support/logger_thread_safe_level.rb
index ba32813d3d0bee24e43ae2c2e1b5f13fae3a963d..52295d7d333bbecc6e231bd4241faad0da3f322e 100644
--- a/activesupport/lib/active_support/logger_thread_safe_level.rb
+++ b/activesupport/lib/active_support/logger_thread_safe_level.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "active_support/concern"
+require "fiber"
 
 module ActiveSupport
   module LoggerThreadSafeLevel # :nodoc:
@@ -11,7 +12,7 @@ def after_initialize
     end
 
     def local_log_id
-      Thread.current.__id__
+      Fiber.current.__id__
     end
 
     def local_level
diff --git a/activesupport/test/logger_test.rb b/activesupport/test/logger_test.rb
index 5efbd10a7d0b90800a50758503236f3f264025a3..1df61a479f2cd5586ee0f73cbf73062d3377b62e 100644
--- a/activesupport/test/logger_test.rb
+++ b/activesupport/test/logger_test.rb
@@ -257,6 +257,50 @@ def test_logger_level_local_thread_safety
     assert_level(Logger::INFO)
   end
 
+  def test_logger_level_main_fiber_safety
+    @logger.level = Logger::INFO
+    assert_level(Logger::INFO)
+
+    fiber = Fiber.new do
+      assert_level(Logger::INFO)
+    end
+
+    @logger.silence(Logger::ERROR) do
+      assert_level(Logger::ERROR)
+      fiber.resume
+    end
+  end
+
+  def test_logger_level_local_fiber_safety
+    @logger.level = Logger::INFO
+    assert_level(Logger::INFO)
+
+    another_fiber = Fiber.new do
+      @logger.silence(Logger::ERROR) do
+        assert_level(Logger::ERROR)
+        @logger.silence(Logger::DEBUG) do
+          assert_level(Logger::DEBUG)
+        end
+      end
+
+      assert_level(Logger::INFO)
+    end
+
+    Fiber.new do
+      @logger.silence(Logger::ERROR) do
+        assert_level(Logger::ERROR)
+        @logger.silence(Logger::DEBUG) do
+          another_fiber.resume
+          assert_level(Logger::DEBUG)
+        end
+      end
+
+      assert_level(Logger::INFO)
+    end.resume
+
+    assert_level(Logger::INFO)
+  end
+
   private
     def level_name(level)
       ::Logger::Severity.constants.find do |severity|