diff --git a/src/item/Item.js b/src/item/Item.js
index 7735930f..93a8652c 100644
--- a/src/item/Item.js
+++ b/src/item/Item.js
@@ -164,10 +164,14 @@ var Item = Base.extend(Callback, /** @lends Item# */{
 		function serialize(fields) {
 			for (var key in fields) {
 				var value = that[key];
-				if (!Base.equals(value, fields[key]))
+				// Allow returned values to mark themselves as default through
+				// the "hidden" _default property. See Style#getLeading()
+				if (!(value && value._default)
+						&& !Base.equals(value, fields[key])) {
 					props[key] = Base.serialize(value, options,
 							// Do not use compact mode for data
 							key !== 'data', dictionary);
+				}
 			}
 		}
 
diff --git a/src/style/Style.js b/src/style/Style.js
index ffff0393..6d72394d 100644
--- a/src/style/Style.js
+++ b/src/style/Style.js
@@ -238,7 +238,13 @@ var Style = Base.extend(new function() {
 	getLeading: function getLeading() {
 		// Override leading to return fontSize * 1.2 by default.
 		var leading = getLeading.base.call(this);
-		return leading != null ? leading : this.getFontSize() * 1.2;
+		if (leading == null) {
+			// Box default leading in a Number, and mark it as default, for
+			// serialization.
+			leading = new Number(this.getFontSize() * 1.2);
+			leading._default = true;
+		}
+		return leading;
 	},
 
 	getFontStyle: function() {