diff --git a/app/src/main/java/be/digitalia/fosdem/widgets/AdapterLinearLayout.java b/app/src/main/java/be/digitalia/fosdem/widgets/AdapterLinearLayout.java
index 7ae0c7e..ec3182b 100644
--- a/app/src/main/java/be/digitalia/fosdem/widgets/AdapterLinearLayout.java
+++ b/app/src/main/java/be/digitalia/fosdem/widgets/AdapterLinearLayout.java
@@ -82,7 +82,7 @@ public class AdapterLinearLayout extends LinearLayout {
 	@Override
 	protected void onDetachedFromWindow() {
 		super.onDetachedFromWindow();
-		if (mAdapter != null) {
+		if ((mAdapter != null) && (mDataSetObserver != null)) {
 			mAdapter.mDataSetObservable.unregisterObserver(mDataSetObserver);
 		}
 		mDataSetObserver = null;