diff --git a/http-core/src/main/scala/org/apache/pekko/http/impl/engine/http2/Http2StreamHandling.scala b/http-core/src/main/scala/org/apache/pekko/http/impl/engine/http2/Http2StreamHandling.scala
index e17ca4dc35..f59037de04 100644
--- a/http-core/src/main/scala/org/apache/pekko/http/impl/engine/http2/Http2StreamHandling.scala
+++ b/http-core/src/main/scala/org/apache/pekko/http/impl/engine/http2/Http2StreamHandling.scala
@@ -358,7 +358,10 @@ private[http2] trait Http2StreamHandling extends GraphStageLogic with LogHelper
       extraInitialWindow: Int) extends ReceivingData {
 
     override protected def onDataFrame(dataFrame: DataFrame): StreamState = {
-      val newData = collectedData ++ dataFrame.payload
+      val newData =
+        if (collectedData.isEmpty) dataFrame.payload
+        else if (dataFrame.payload.isEmpty) collectedData
+        else collectedData ++ dataFrame.payload
 
       if (dataFrame.endStream) {
         totalBufferedData -= newData.length