diff --git a/tests/unit/style/size_of.rs b/tests/unit/style/size_of.rs
index c0b14276c24..9d501d7ed99 100644
--- a/tests/unit/style/size_of.rs
+++ b/tests/unit/style/size_of.rs
@@ -5,6 +5,7 @@
 use style::properties;
 
 size_of_test!(test_size_of_property_declaration, properties::PropertyDeclaration, 32);
+size_of_test!(test_size_of_parsed_declaration, properties::ParsedDeclaration, 456);
 
 #[test]
 fn size_of_specified_values() {
diff --git a/tests/unit/stylo/size_of.rs b/tests/unit/stylo/size_of.rs
index ce2e076ba86..2e0087fc4c6 100644
--- a/tests/unit/stylo/size_of.rs
+++ b/tests/unit/stylo/size_of.rs
@@ -20,6 +20,7 @@ fn size_of_selectors_dummy_types() {
 }
 
 size_of_test!(test_size_of_property_declaration, style::properties::PropertyDeclaration, 32);
+size_of_test!(test_size_of_parsed_declaration, style::properties::ParsedDeclaration, 584);
 
 #[test]
 fn size_of_specified_values() {