diff --git a/lib/pstore.rb b/lib/pstore.rb
index 0d89e75..8c32d78 100644
--- a/lib/pstore.rb
+++ b/lib/pstore.rb
@@ -439,7 +439,7 @@ def [](key)
   def fetch(key, default=PStore::Error)
     in_transaction
     unless @table.key? key
-      if default == PStore::Error
+      if PStore::Error.equal?(default)
         raise PStore::Error, format("undefined key '%s'", key)
       else
         return default
diff --git a/test/test_pstore.rb b/test/test_pstore.rb
index 33801e1..98d4459 100644
--- a/test/test_pstore.rb
+++ b/test/test_pstore.rb
@@ -235,4 +235,13 @@ def test_commit_targets_the_owning_store
   ensure
     File.unlink(second_file) rescue nil
   end
+
+  def test_fetch_compares_missing_default_by_identity
+    default = Object.new
+    def default.==(_other)
+      true
+    end
+
+    assert_same(default, @pstore.transaction(true) { @pstore.fetch(:missing, default) })
+  end
 end