diff --git a/sql/src/main/java/org/apache/druid/sql/calcite/rel/DruidQuery.java b/sql/src/main/java/org/apache/druid/sql/calcite/rel/DruidQuery.java
index 1cf79b6dc123..b5c5ce608844 100644
--- a/sql/src/main/java/org/apache/druid/sql/calcite/rel/DruidQuery.java
+++ b/sql/src/main/java/org/apache/druid/sql/calcite/rel/DruidQuery.java
@@ -277,6 +277,7 @@ public static DruidQuery fromPartialQuery(
 
     if (partialQuery.getWindow() != null) {
       if (plannerContext.featureAvailable(EngineFeature.WINDOW_FUNCTIONS)) {
+        assert (virtualColumnRegistry.isEmpty());
         windowing = Preconditions.checkNotNull(
             Windowing.fromCalciteStuff(
                 partialQuery,
diff --git a/sql/src/main/java/org/apache/druid/sql/calcite/rel/Windowing.java b/sql/src/main/java/org/apache/druid/sql/calcite/rel/Windowing.java
index d94b3bb3b19f..bc35b5412d8a 100644
--- a/sql/src/main/java/org/apache/druid/sql/calcite/rel/Windowing.java
+++ b/sql/src/main/java/org/apache/druid/sql/calcite/rel/Windowing.java
@@ -142,8 +142,6 @@ public static Windowing fromCalciteStuff(
     }
 
     for (int i = 0; i < window.groups.size(); ++i) {
-
-      // FIXME: I think this should be recreated after every group
       VirtualColumnRegistry virtualColumnRegistry = VirtualColumnRegistry.create(
           sourceRowSignature,
           plannerContext.getExpressionParser(),