diff --git a/spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala b/spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala
index 41a69f7a32..d91ae5e4d7 100644
--- a/spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala
+++ b/spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala
@@ -2535,8 +2535,12 @@ object QueryPlanSerde extends Logging with ShimQueryPlanSerde with CometExprShim
           }
         }.toArray
 
-        val windowExprProto = winExprs.map(windowExprToProto(_, output))
+        if (winExprs.length != windowExpression.length) {
+          withInfo(op, "Unsupported window expression(s)")
+          return None
+        }
 
+        val windowExprProto = winExprs.map(windowExprToProto(_, output))
         val partitionExprs = partitionSpec.map(exprToProto(_, child.output))
 
         val sortOrders = orderSpec.map(exprToProto(_, child.output))
diff --git a/spark/src/test/scala/org/apache/comet/exec/CometExecSuite.scala b/spark/src/test/scala/org/apache/comet/exec/CometExecSuite.scala
index e657af9b9d..4887be51e7 100644
--- a/spark/src/test/scala/org/apache/comet/exec/CometExecSuite.scala
+++ b/spark/src/test/scala/org/apache/comet/exec/CometExecSuite.scala
@@ -63,6 +63,15 @@ class CometExecSuite extends CometTestBase {
     }
   }
 
+  test("sum/avg over window should fall back to Spark") {
+    checkAnswer(
+      spark.sql("select sum(a) over () from values 1.0, 2.0, 3.0 T(a)"),
+      Row(6.0) :: Row(6.0) :: Row(6.0) :: Nil)
+    checkAnswer(
+      spark.sql("select avg(a) over () from values 1.0, 2.0, 3.0 T(a)"),
+      Row(2.0) :: Row(2.0) :: Row(2.0) :: Nil)
+  }
+
   test("fix CometNativeExec.doCanonicalize for ReusedExchangeExec") {
     assume(isSpark34Plus, "ChunkedByteBuffer is not serializable before Spark 3.4+")
     withSQLConf(