diff --git a/metadaptb.go b/metadaptb.go
index 18776da..fdf2ba2 100644
--- a/metadaptb.go
+++ b/metadaptb.go
@@ -126,7 +126,7 @@ type Stream interface {
 }
 
 func encodeMessageB(writer io.Writer, sizeLimit int64, method uint16, data []byte) error {
-	if len(data) > int(sizeLimit) {
+	if int64(len(data)) > sizeLimit {
 		return ErrPayloadTooLarge
 	}
 	buffer := make([]byte, 10 + len(data))