diff --git a/spec/lib/vault/rails/json_serializer_spec.rb b/spec/lib/vault/rails/json_serializer_spec.rb
index 645fb0aa..43661ddb 100644
--- a/spec/lib/vault/rails/json_serializer_spec.rb
+++ b/spec/lib/vault/rails/json_serializer_spec.rb
@@ -34,7 +34,7 @@
       it { is_expected.to eq(nil) }
     end
 
-    context "with an empty string" do
+    context "with an empty string (only possible if column has a default)" do
       let(:raw) { "" }
       it { is_expected.to eq(nil) }
     end