diff --git a/opentasks-contract/src/main/java/org/dmfs/tasks/contract/TaskContract.java b/opentasks-contract/src/main/java/org/dmfs/tasks/contract/TaskContract.java
index 5fa5052ee..9705cc539 100644
--- a/opentasks-contract/src/main/java/org/dmfs/tasks/contract/TaskContract.java
+++ b/opentasks-contract/src/main/java/org/dmfs/tasks/contract/TaskContract.java
@@ -1491,8 +1491,8 @@ interface Contact extends PropertyColumns
         /**
          * Relations of a task.
          * <p>
-         * When writing a relation, exactly one of {@link #RELATED_ID} or {@link #RELATED_UID}. {@link #RELATED_CONTENT_URI} will be
-         * populated automatically if possible.
+         * When writing a relation, exactly one of {@link #RELATED_ID} or {@link #RELATED_UID} must be present. The missing value and {@link
+         * #RELATED_CONTENT_URI} will be populated automatically if possible.
          */
         interface Relation extends PropertyColumns
         {
@@ -1511,7 +1511,7 @@ interface Relation extends PropertyColumns
             String RELATED_ID = DATA1;
 
             /**
-             * The relation type. This must be the one of the {@code RELTYPE_*} values.
+             * The relation type. This must be one of the {@code RELTYPE_*} values.
              * <p>
              * Value: int
              * </p>
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java
index 114ab38ec..593e1e40d 100644
--- a/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java
@@ -36,7 +36,7 @@
 public final class RelationData extends DelegatingRowData<TaskContract.Properties>
 {
     public RelationData(@NonNull RowSnapshot<TaskContract.Tasks> relatingTask,
-                        @NonNull int relType,
+                        int relType,
                         @NonNull RowSnapshot<TaskContract.Tasks> relatedTask)
     {
         super(new Composite<>(
@@ -47,7 +47,7 @@ public RelationData(@NonNull RowSnapshot<TaskContract.Tasks> relatingTask,
 
 
     public RelationData(@NonNull RowSnapshot<TaskContract.Tasks> relatingTask,
-                        @NonNull int relType,
+                        int relType,
                         @NonNull CharSequence relatedTaskUid)
     {
         super(new Composite<>(