diff --git a/common/crypto/auth.go b/common/crypto/auth.go
index 65bba5e26c3..f8ba55b8dce 100644
--- a/common/crypto/auth.go
+++ b/common/crypto/auth.go
@@ -178,7 +178,7 @@ func (r *AuthenticationReader) readInternal(soft bool, mb *buf.MultiBuffer) erro
 		return errSoft
 	}
 
-	if size <= buf.Size {
+	if effectiveSize <= buf.Size {
 		b, err := r.readBuffer(effectiveSize, int32(padding))
 		if err != nil {
 			return err