diff --git a/lib/double_entry/line_metadata.rb b/lib/double_entry/line_metadata.rb
index 351f19a..c3746d8 100644
--- a/lib/double_entry/line_metadata.rb
+++ b/lib/double_entry/line_metadata.rb
@@ -13,6 +13,6 @@ def self.dump(symbol)
     end
 
     belongs_to :line
-    serialize :key, SymbolWrapper
+    serialize :key, coder: DoubleEntry::LineMetadata::SymbolWrapper
   end
 end