diff --git a/src/syscall/zx/fidl/encoding_new.go b/src/syscall/zx/fidl/encoding_new.go
index 0eae4d6..5e84f32 100644
--- a/src/syscall/zx/fidl/encoding_new.go
+++ b/src/syscall/zx/fidl/encoding_new.go
@@ -1244,7 +1244,12 @@
 	return m.size
 }
 
-const envelopeSize = 16
+func envelopeSize(ctx MarshalerContext) int {
+	if ctx.UseV2WireFormat {
+		return 8
+	}
+	return 16
+}
 
 type envelopeHeader struct {
 	byteValue   []byte
@@ -1396,14 +1401,16 @@
 		in.handleInfos = usedHandles
 	}
 
+	if header.isInline {
+		unknownData := in.buffer[offset:][:4]
+		return unknownData, unknownHandles, nil
+	}
+
 	start, err := in.newObject(int(header.byteCount), depth)
 	if err != nil {
 		return nil, nil, err
 	}
 
-	if err != nil {
-		return nil, nil, err
-	}
 	unknownData := in.buffer[start:][:header.byteCount]
 
 	return unknownData, unknownHandles, nil
@@ -1442,6 +1449,7 @@
 	return true, nil
 }
 
+// TODO(fxbug.dev/81180) Validate inline size <= 4 if header has inline bit set.
 func unmarshalEnvelope(ctx MarshalerContext, m Marshaler, in *decoder, offset int, depth int, v unsafevalue.Value, mode unmarshalEnvelopeMode) (bool, error) {
 	startingFrom := in.nextObject
 	unclaimedHandles := uint32(len(in.handleInfos))
@@ -1534,7 +1542,7 @@
 	}
 
 	// Encode in the out-of-line object.
-	outOfLineOffset, err := out.newObject(int(maxOrdinal)*envelopeSize, depth)
+	outOfLineOffset, err := out.newObject(int(maxOrdinal)*envelopeSize(ctx), depth)
 	if err != nil {
 		return err
 	}
@@ -1612,7 +1620,7 @@
 		index              = 0
 		unknownData map[uint64]UnknownData
 	)
-	outOfLineOffset, err := in.newObject(int(maxOrdinal)*envelopeSize, depth)
+	outOfLineOffset, err := in.newObject(int(maxOrdinal)*envelopeSize(ctx), depth)
 	if err != nil {
 		return err
 	}
@@ -1643,7 +1651,7 @@
 			}
 		}
 		ordinal++
-		envelopeOffset += 16
+		envelopeOffset += envelopeSize(ctx)
 		if fieldKnown {
 			index++
 		}