diff --git a/errors.go b/errors.go
new file mode 100755
index 000000000..31d27af0d
--- /dev/null
+++ b/errors.go
@@ -0,0 +1,51 @@
+// Copyright (C) 2014 The Protocol Authors.
+
+package protocol
+
+import (
+	"errors"
+)
+
+const (
+	ecNoError int32 = iota
+	ecGeneric
+	ecNoSuchFile
+	ecInvalid
+)
+
+var (
+	ErrNoError    error = nil
+	ErrGeneric          = errors.New("generic error")
+	ErrNoSuchFile       = errors.New("no such file")
+	ErrInvalid          = errors.New("file is invalid")
+)
+
+var lookupError = map[int32]error{
+	ecNoError:    ErrNoError,
+	ecGeneric:    ErrGeneric,
+	ecNoSuchFile: ErrNoSuchFile,
+	ecInvalid:    ErrInvalid,
+}
+
+var lookupCode = map[error]int32{
+	ErrNoError:    ecNoError,
+	ErrGeneric:    ecGeneric,
+	ErrNoSuchFile: ecNoSuchFile,
+	ErrInvalid:    ecInvalid,
+}
+
+func codeToError(errcode int32) error {
+	err, ok := lookupError[errcode]
+	if !ok {
+		return ErrGeneric
+	}
+	return err
+}
+
+func errorToCode(err error) int32 {
+	code, ok := lookupCode[err]
+	if !ok {
+		return ecGeneric
+	}
+	return code
+}
diff --git a/protocol.go b/protocol.go
index 48d43995a..d46d70036 100644
--- a/protocol.go
+++ b/protocol.go
@@ -497,10 +497,11 @@ func filterIndexMessageFiles(fs []FileInfo) []FileInfo {
 }
 
 func (c *rawConnection) handleRequest(msgID int, req RequestMessage) {
-	data, _ := c.receiver.Request(c.id, req.Folder, req.Name, int64(req.Offset), int(req.Size), req.Hash, req.Flags, req.Options)
+	data, err := c.receiver.Request(c.id, req.Folder, req.Name, int64(req.Offset), int(req.Size), req.Hash, req.Flags, req.Options)
 
 	c.send(msgID, messageTypeResponse, ResponseMessage{
 		Data: data,
+		Code: errorToCode(err),
 	})
 }
 
@@ -508,7 +509,7 @@ func (c *rawConnection) handleResponse(msgID int, resp ResponseMessage) {
 	c.awaitingMut.Lock()
 	if rc := c.awaiting[msgID]; rc != nil {
 		c.awaiting[msgID] = nil
-		rc <- asyncResult{resp.Data, nil}
+		rc <- asyncResult{resp.Data, codeToError(resp.Code)}
 		close(rc)
 	}
 	c.awaitingMut.Unlock()