diff --git a/app-sample/src/main/java/io/noties/markwon/app/samples/parser/CustomHeadingParserSample.kt b/app-sample/src/main/java/io/noties/markwon/app/samples/parser/CustomHeadingParserSample.kt
index 214bcae2..ea54755b 100644
--- a/app-sample/src/main/java/io/noties/markwon/app/samples/parser/CustomHeadingParserSample.kt
+++ b/app-sample/src/main/java/io/noties/markwon/app/samples/parser/CustomHeadingParserSample.kt
@@ -39,9 +39,9 @@ class CustomHeadingParserSample : MarkwonTextViewSample() {
   }
 
   object MyHeadingBlockParserFactory : BlockParserFactory {
-    override fun tryStart(state: ParserState, matchedBlockParser: MatchedBlockParser): BlockStart {
+    override fun tryStart(state: ParserState, matchedBlockParser: MatchedBlockParser): BlockStart? {
       // TODO("Not yet implemented")
-      return BlockStart.none()
+      return null
     }
   }
 }
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