diff --git a/serialization.nim b/serialization.nim
index d86b8de..c5fbe81 100644
--- a/serialization.nim
+++ b/serialization.nim
@@ -121,3 +121,8 @@ template borrowSerialization*(Alias: distinct type,
     mixin readValue
     value = Alias reader.readValue(OriginalType)
 
+template appendValue*(stream: OutputStreamVar, Format: type, value: auto) =
+  mixin WriterType, init, writeValue
+  var writer = init(WriterType(Format), stream)
+  writeValue writer, value
+
diff --git a/serialization/errors.nim b/serialization/errors.nim
index 42cf615..2c5cf04 100644
--- a/serialization/errors.nim
+++ b/serialization/errors.nim
@@ -2,6 +2,6 @@ type
   SerializationError* = object of CatchableError
   UnexpectedEofError* = object of SerializationError
 
-method formatMsg*(err: ref SerializationError, filename: string): string {.base.} =
+method formatMsg*(err: ref SerializationError, filename: string): string {.gcsafe, base.} =
   "Serialisation error while processing " & filename