diff --git a/src/util/guid.cpp b/src/util/guid.cpp
index f9580458c..97f20607f 100644
--- a/src/util/guid.cpp
+++ b/src/util/guid.cpp
@@ -16,7 +16,7 @@ std::string MyGUID::base64() const
 	return base64_encode(std::string_view(&bytes[0], bytes.size()));
 }
 
-void MyGUID::serialize(std::ostringstream &os) const
+void MyGUID::serialize(std::ostream &os) const
 {
 	os.write(&bytes[0], bytes.size());
 }
diff --git a/src/util/guid.h b/src/util/guid.h
index 87ea2ccf7..8bfff7454 100644
--- a/src/util/guid.h
+++ b/src/util/guid.h
@@ -17,15 +17,17 @@ class ServerEnvironment;
  * It is global because it stays valid forever.
  * It is unique because there are no collisions.
  */
-struct MyGUID {
+struct MyGUID
+{
 	std::array<char, 16> bytes;
 
 	std::string base64() const;
-	void serialize(std::ostringstream &os) const;
+	void serialize(std::ostream &os) const;
 	void deSerialize(std::istream &is);
 };
 
-class GUIDGenerator {
+class GUIDGenerator
+{
 	DISABLE_CLASS_COPY(GUIDGenerator)
 
 public: