diff --git a/proto/decode.go b/proto/decode.go
index e1177b82..2e2ce8dd 100644
--- a/proto/decode.go
+++ b/proto/decode.go
@@ -99,7 +99,7 @@ func (o UnmarshalOptions) unmarshal(b []byte, message Message) (out protoiface.U
 	if err != nil {
 		return out, err
 	}
-	if allowPartial {
+	if allowPartial || out.Initialized {
 		return out, nil
 	}
 	return out, isInitialized(m)