diff --git a/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/internal/boxes/FakeContentBox.java b/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/internal/boxes/FakeContentBox.java
index e467976..c93bb91 100644
--- a/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/internal/boxes/FakeContentBox.java
+++ b/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/internal/boxes/FakeContentBox.java
@@ -122,4 +122,14 @@
 		return startOffset;
 	}
 
+	@Override
+	public void setParent(final IBox parent) {
+		// ignore
+	}
+
+	@Override
+	public IBox getParent() {
+		return null;
+	}
+
 }
diff --git a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/IContentBox.java b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/IContentBox.java
index 656eb84..cb443f4 100644
--- a/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/IContentBox.java
+++ b/org.eclipse.vex.core/src/org/eclipse/vex/core/internal/boxes/IContentBox.java
@@ -17,7 +17,7 @@
 /**
  * @author Florian Thienel
  */
-public interface IContentBox extends IBox {
+public interface IContentBox extends IChildBox {
 
 	int getStartOffset();