diff --git a/plc4j/drivers/iec-60870/src/main/java/org/apache/plc4x/java/iec608705104/readwrite/Iec60870514PlcDriver.java b/plc4j/drivers/iec-60870/src/main/java/org/apache/plc4x/java/iec608705104/readwrite/Iec60870514PlcDriver.java
index 5beb83dfdaf..00a5caf4413 100644
--- a/plc4j/drivers/iec-60870/src/main/java/org/apache/plc4x/java/iec608705104/readwrite/Iec60870514PlcDriver.java
+++ b/plc4j/drivers/iec-60870/src/main/java/org/apache/plc4x/java/iec608705104/readwrite/Iec60870514PlcDriver.java
@@ -114,7 +114,7 @@ public static class ByteLengthEstimator implements ToIntFunction<ByteBuf> {
         @Override
         public int applyAsInt(ByteBuf byteBuf) {
             if (byteBuf.readableBytes() >= 2) {
-                return byteBuf.getUnsignedByte( 1) + 2;
+                return byteBuf.getUnsignedByte( byteBuf.readerIndex() + 1) + 2;
             }
             return -1;
         }