diff --git a/omniNotes/src/main/java/it/feio/android/omninotes/db/DbHelper.java b/omniNotes/src/main/java/it/feio/android/omninotes/db/DbHelper.java
index 4cf182197..530291dbd 100644
--- a/omniNotes/src/main/java/it/feio/android/omninotes/db/DbHelper.java
+++ b/omniNotes/src/main/java/it/feio/android/omninotes/db/DbHelper.java
@@ -906,7 +906,7 @@ public long deleteCategory(Category category) {
     SQLiteDatabase db = getDatabase(true);
     // Un-categorize notes associated with this category
     ContentValues values = new ContentValues();
-    values.put(KEY_CATEGORY, "");
+    values.putNull(KEY_CATEGORY);
 
     // Updating row
     db.update(TABLE_NOTES, values, KEY_CATEGORY + " = ?",