diff --git a/acceptance/cases/models/binary_identifiers.rb b/acceptance/cases/models/binary_identifiers.rb
index 7c1920c0..4db9d74a 100644
--- a/acceptance/cases/models/binary_identifiers.rb
+++ b/acceptance/cases/models/binary_identifiers.rb
@@ -66,6 +66,11 @@ def test_includes_works
 
       user = User.all.includes(:projects).first
       assert user
+      project_count = 0
+      user.projects.each do |_|
+        project_count += 1
+      end
+      assert_equal 3, project_count
       assert_equal 3, user.projects.count
     end
 
diff --git a/acceptance/models/binary_project.rb b/acceptance/models/binary_project.rb
index 8e817b37..e09967a9 100644
--- a/acceptance/models/binary_project.rb
+++ b/acceptance/models/binary_project.rb
@@ -6,6 +6,8 @@
 
 # frozen_string_literal: true
 
+require_relative 'string_io'
+
 class BinaryProject < ActiveRecord::Base
   belongs_to :owner, class_name: 'User'
 
diff --git a/acceptance/models/string_io.rb b/acceptance/models/string_io.rb
new file mode 100644
index 00000000..9de8c1e2
--- /dev/null
+++ b/acceptance/models/string_io.rb
@@ -0,0 +1,28 @@
+# Copyright 2025 Google LLC
+#
+# Use of this source code is governed by an MIT-style
+# license that can be found in the LICENSE file or at
+# https://opensource.org/licenses/MIT.
+
+# frozen_string_literal: true
+
+# Add equality and hash functions to StringIO to use it for sets.
+class StringIO
+  def ==(o)
+    o.class == self.class && self.to_base64 == o.to_base64
+  end
+
+  def eql?(o)
+    self == o
+  end
+
+  def hash
+    to_base64.hash
+  end
+
+  def to_base64
+    self.rewind
+    value = self.read
+    Base64.strict_encode64 value.force_encoding("ASCII-8BIT")
+  end
+end
diff --git a/acceptance/models/user.rb b/acceptance/models/user.rb
index f5fbd330..54608d4e 100644
--- a/acceptance/models/user.rb
+++ b/acceptance/models/user.rb
@@ -6,6 +6,8 @@
 
 # frozen_string_literal: true
 
+require_relative 'string_io'
+
 class User < ActiveRecord::Base
   has_many :binary_projects, foreign_key: :owner_id
 
diff --git a/test/activerecord_spanner_mock_server/models/binary_project.rb b/test/activerecord_spanner_mock_server/models/binary_project.rb
index 8e817b37..d34ca894 100644
--- a/test/activerecord_spanner_mock_server/models/binary_project.rb
+++ b/test/activerecord_spanner_mock_server/models/binary_project.rb
@@ -6,6 +6,8 @@
 
 # frozen_string_literal: true
 
+require_relative "string_io"
+
 class BinaryProject < ActiveRecord::Base
   belongs_to :owner, class_name: 'User'
 
diff --git a/test/activerecord_spanner_mock_server/models/string_io.rb b/test/activerecord_spanner_mock_server/models/string_io.rb
new file mode 100644
index 00000000..22e9cfa4
--- /dev/null
+++ b/test/activerecord_spanner_mock_server/models/string_io.rb
@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+class StringIO
+  def ==(o)
+    o.class == self.class && self.to_base64 == o.to_base64
+  end
+
+  def eql?(o)
+    self == o
+  end
+
+  def hash
+    to_base64.hash
+  end
+
+  def to_base64
+    self.rewind
+    value = self.read
+    Base64.strict_encode64 value.force_encoding("ASCII-8BIT")
+  end
+end
diff --git a/test/activerecord_spanner_mock_server/models/user.rb b/test/activerecord_spanner_mock_server/models/user.rb
index f5fbd330..0f5b6e8f 100644
--- a/test/activerecord_spanner_mock_server/models/user.rb
+++ b/test/activerecord_spanner_mock_server/models/user.rb
@@ -6,6 +6,8 @@
 
 # frozen_string_literal: true
 
+require_relative "string_io"
+
 class User < ActiveRecord::Base
   has_many :binary_projects, foreign_key: :owner_id
 
diff --git a/test/activerecord_spanner_mock_server/spanner_active_record_with_mock_server_test.rb b/test/activerecord_spanner_mock_server/spanner_active_record_with_mock_server_test.rb
index 2c03f099..4beff9ae 100644
--- a/test/activerecord_spanner_mock_server/spanner_active_record_with_mock_server_test.rb
+++ b/test/activerecord_spanner_mock_server/spanner_active_record_with_mock_server_test.rb
@@ -1317,6 +1317,61 @@ def test_binary_id_association
       assert_equal to_base64(user.id), mutation.insert.values[0][3]
     end
 
+    def test_binary_id_association_includes
+      col_id = Field.new name: "id", type: Type.new(code: TypeCode::BYTES)
+      col_email = Field.new name: "email", type: Type.new(code: TypeCode::STRING)
+      col_full_name = Field.new name: "full_name", type: Type.new(code: TypeCode::STRING)
+
+      metadata = ResultSetMetadata.new row_type: StructType.new
+      metadata.row_type.fields.push col_id, col_email, col_full_name
+      result_set = ResultSet.new metadata: metadata
+
+      user_id = to_base64(StringIO.new(SecureRandom.random_bytes(16)))
+      row = ListValue.new
+      row.values.push(
+        Value.new(string_value: user_id),
+        Value.new(string_value: "test_user@example.com"),
+        Value.new(string_value: "Test User")
+      )
+      result_set.rows.push row
+      statement_result = StatementResult.new(result_set)
+
+      sql = "SELECT `users`.* FROM `users` ORDER BY `users`.`id` ASC LIMIT @p1"
+      @mock.put_statement_result sql, statement_result
+
+      col_id = Field.new name: "id", type: Type.new(code: TypeCode::BYTES)
+      col_name = Field.new name: "name", type: Type.new(code: TypeCode::STRING)
+      col_description = Field.new name: "description", type: Type.new(code: TypeCode::STRING)
+      col_owner = Field.new name: "owner_id", type: Type.new(code: TypeCode::BYTES)
+
+      metadata = ResultSetMetadata.new row_type: StructType.new
+      metadata.row_type.fields.push col_id, col_name, col_description, col_owner
+      result_set = ResultSet.new metadata: metadata
+
+      project_count = 3
+      (1..project_count).each { |i|
+        row = ListValue.new
+        row.values.push(
+          Value.new(string_value: to_base64(StringIO.new(SecureRandom.random_bytes(16)))),
+          Value.new(string_value: "Test Project #{i}"),
+          Value.new(string_value: "Test Project Description #{i}"),
+          Value.new(string_value: user_id)
+        )
+        result_set.rows.push row
+      }
+      statement_result = StatementResult.new(result_set)
+      projects_sql = "SELECT `binary_projects`.* FROM `binary_projects` WHERE `binary_projects`.`owner_id` = @p1"
+      @mock.put_statement_result projects_sql, statement_result
+
+      users = User.all.includes(:binary_projects)
+      u1 = users.first
+      found = 0
+      u1.binary_projects.each do |_|
+        found += 1
+      end
+      assert_equal project_count, found
+    end
+
     def test_skip_binary_deserialization
       ENV["SPANNER_BYTES_DESERIALIZE_DISABLED"] = "true"
       begin