diff --git a/lib/dolly/document_state.rb b/lib/dolly/document_state.rb
index 3bb1ca2..f5ad5fc 100644
--- a/lib/dolly/document_state.rb
+++ b/lib/dolly/document_state.rb
@@ -17,7 +17,7 @@ def save!
     end
 
     def update_properties(properties)
-      properties.each(&update_attribute)
+      properties.deep_symbolize_keys.each(&update_attribute)
     end
 
     def update_properties!(properties)