diff --git a/yaml/dom.nim b/yaml/dom.nim
index 454f508..19d7a57 100644
--- a/yaml/dom.nim
+++ b/yaml/dom.nim
@@ -22,7 +22,9 @@
 import tables, streams, hashes, sets, strutils
 import stream, taglib, serialization, private/internal, parser,
        presenter
-
+       
+when defined(nimNoNil):
+    {.experimental: "notnil".}
 type
   YamlNodeKind* = enum
     yScalar, yMapping, ySequence
diff --git a/yaml/stream.nim b/yaml/stream.nim
index e4ceb4c..b107a65 100644
--- a/yaml/stream.nim
+++ b/yaml/stream.nim
@@ -1,4 +1,4 @@
-#            NimYAML - YAML implementation in Nim
+    #            NimYAML - YAML implementation in Nim
 #        (c) Copyright 2016 Felix Krause
 #
 #    See the file "copying.txt", included in this
@@ -15,6 +15,9 @@
 import hashes
 import private/internal, taglib
 
+when defined(nimNoNil):
+    {.experimental: "notnil".}
+    
 when defined(yamlScalarRepInd):
   type ScalarRepresentationIndicator* = enum
     srPlain, srSingleQuoted, srDoubleQuoted, srLiteral, srFolded