diff --git a/src/include/planner/operator/schema.h b/src/include/planner/operator/schema.h
index 22769a455..28d5c892e 100644
--- a/src/include/planner/operator/schema.h
+++ b/src/include/planner/operator/schema.h
@@ -38,8 +38,10 @@ class FactorizationGroup {
     double getMultiplier() const { return cardinalityMultiplier; }
 
     void insertExpression(const std::shared_ptr<binder::Expression>& expression) {
-        DASSERT(!expressionNameToPos.contains(expression->getUniqueName()));
-        expressionNameToPos.insert({expression->getUniqueName(), expressions.size()});
+        // A projection keeps out-of-scope expressions in their groups, so one with the same unique
+        // name may already be here, e.g. an ORDER BY key a WITH dropped. The new expression gets
+        // its own position: the old one's is still written by the operator that produced it.
+        expressionNameToPos.insert_or_assign(expression->getUniqueName(), expressions.size());
         expressions.push_back(expression);
     }
     binder::expression_vector getExpressions() const { return expressions; }
diff --git a/test/test_files/order_by/order_by_key_repeated.test b/test/test_files/order_by/order_by_key_repeated.test
new file mode 100644
index 000000000..25f4ec720
--- /dev/null
+++ b/test/test_files/order_by/order_by_key_repeated.test
@@ -0,0 +1,21 @@
+-DATASET CSV empty
+
+--
+
+-CASE ProjectionRepeatsDiscardedOrderByKey
+-LOOP i 1 2000
+-STATEMENT UNWIND [10, 20, NULL, 5] AS x WITH x ORDER BY x + x SKIP 0 RETURN x + x AS y
+-CHECK_ORDER
+---- 4
+10
+20
+40
+
+-STATEMENT UNWIND [10, 20, NULL, 5] AS x WITH x ORDER BY x * x SKIP 0 RETURN x * x AS y
+-CHECK_ORDER
+---- 4
+25
+100
+400
+
+-ENDLOOP