diff --git a/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/serializer/impl/PartialSerializer.java b/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/serializer/impl/PartialSerializer.java
index fe60a0c36..6e9def557 100644
--- a/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/serializer/impl/PartialSerializer.java
+++ b/org.eclipse.xtext.ide/src/org/eclipse/xtext/ide/serializer/impl/PartialSerializer.java
@@ -335,12 +335,14 @@ public class PartialSerializer {
 		EStructuralFeature feature = change.getFeature();
 		IFeatureInfo featureInfo = constraint.getFeatures()[owner.eClass().getFeatureID(feature)];
 		List<IConstraintElement> assignments = featureInfo.getAssignments();
-		if (assignments.size() != 1) {
+		if (assignments.isEmpty()) {
 			ValueTransient valueTransient = transientValues.isValueTransient(owner, feature);
 			if (valueTransient == ValueTransient.YES) {
 				return result;
 			}
 			return null;
+		} else if (assignments.size() != 1) {
+			return null;
 		}
 		boolean optional = assignments.get(0).isOptional();
 		IAstRegion featureRegion = findRegion(ownerRegion, change);