diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1e57c41..9eb0340 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ### 2.6.1 (Next)
 
 * [#45](https://github.com/mongoid/mongoid-grid_fs/pull/45): Encode stored file bytes rather than the model description in Base64 and data URIs - [@yudho](https://github.com/yudho), [@dblock](https://github.com/dblock).
+* [#48](https://github.com/mongoid/mongoid-grid_fs/pull/48): Check for the specific legacy BSON classes instead of the Moped namespace - [@jeremy6d](https://github.com/jeremy6d), [@dblock](https://github.com/dblock).
 * [#86](https://github.com/mongoid/mongoid-grid_fs/pull/86): Expand persisted GridFS coverage for streaming, upload failures, namespaces, attributes, queries, historical records without `updateDate`, and Rails responses - [@dblock](https://github.com/dblock).
 * [#85](https://github.com/mongoid/mongoid-grid_fs/pull/85): Report test coverage to Coveralls and update CI badges - [@dblock](https://github.com/dblock).
 * [#84](https://github.com/mongoid/mongoid-grid_fs/pull/84): Migrate Danger to danger-pr-comment workflows - [@dblock](https://github.com/dblock).
diff --git a/lib/mongoid/grid_fs.rb b/lib/mongoid/grid_fs.rb
index 63ed8f3..1dcf1c7 100644
--- a/lib/mongoid/grid_fs.rb
+++ b/lib/mongoid/grid_fs.rb
@@ -152,7 +152,7 @@ def put(readable, attributes = {})
         end
 
         def binary_for(*buf)
-          if defined?(Moped::BSON)
+          if defined?(Moped::BSON::Binary)
             Moped::BSON::Binary.new(:generic, buf.join)
           else
             BSON::Binary.new(buf.join, :generic)
@@ -415,7 +415,7 @@ def self.build_chunk_model_for(namespace)
         store_in collection: "#{prefix}.chunks"
 
         field(:n, type: Integer, default: 0)
-        field(:data, type: (defined?(Moped::BSON) ? Moped::BSON::Binary : BSON::Binary))
+        field(:data, type: (defined?(Moped::BSON::Binary) ? Moped::BSON::Binary : BSON::Binary))
 
         belongs_to(:file, foreign_key: :files_id, class_name: file_model_name)
 
diff --git a/test/bson_compatibility_test.rb b/test/bson_compatibility_test.rb
new file mode 100644
index 0000000..6257af4
--- /dev/null
+++ b/test/bson_compatibility_test.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require_relative 'helper'
+require 'open3'
+require 'rbconfig'
+
+class BsonCompatibilityTest < Minitest::Test
+  def test_moped_namespace_without_legacy_binary_uses_modern_bson
+    script = <<~RUBY
+      require 'logger'
+      require 'mongoid'
+      Object.const_set(:Moped, Module.new) unless defined?(Moped)
+      Moped.const_set(:BSON, Module.new) unless defined?(Moped::BSON)
+      require 'mongoid/grid_fs'
+      namespace = Mongoid::GridFs.namespace_for(:bsoncompatibility)
+      binary = namespace.binary_for("one", "two")
+      abort "wrong binary type" unless binary.is_a?(BSON::Binary)
+      abort "wrong bytes" unless binary.data == "onetwo"
+      abort "wrong field type" unless namespace.chunk_model.fields.fetch("data").type == BSON::Binary
+    RUBY
+
+    output, status = Open3.capture2e(RbConfig.ruby, '-Ilib', '-e', script)
+    assert status.success?, output
+  end
+end
diff --git a/test/mongoid-grid_fs_test.rb b/test/mongoid-grid_fs_test.rb
index b6613e5..ea040d5 100644
--- a/test/mongoid-grid_fs_test.rb
+++ b/test/mongoid-grid_fs_test.rb
@@ -230,7 +230,7 @@
 protected
 
   def object_id_re
-    object_id = defined?(Moped::BSON) ? Moped::BSON::ObjectId.new : BSON::ObjectId.new
+    object_id = defined?(Moped::BSON::ObjectId) ? Moped::BSON::ObjectId.new : BSON::ObjectId.new
 
     / \w{#{ object_id.to_s.size }} /iomx
   end