diff --git a/src_v2/parser/parser_internals.nim b/src_v2/parser/parser_internals.nim
index 3b8a887..cab6997 100644
--- a/src_v2/parser/parser_internals.nim
+++ b/src_v2/parser/parser_internals.nim
@@ -114,7 +114,9 @@ proc str*(expectedString: string): parserFnT {.inline.} =
 # -- Parsing API
 
 proc optional*(parserFn: parserFnT): parserFnT {.inline.} =
-  ## Create a
+  ## Creates parser function with a nested `parserFn`.
+  ## Continue on succesful parser
+  ## Ignores failing parsers
   return proc(parser: Parser): ParserResult =
     let newParser = parserFn(parser)
 
@@ -271,3 +273,8 @@ when isMainModule:
     assert initParserResult("12").flatMap(ch1).isStreamCompleted() == false
     assert initParserResult("").flatMap(ch1).isStreamCompleted() == false
     assert testParser123.flatMap(str("123")).isStreamCompleted() == true
+
+  block testParsingApi:
+    # Optional
+    assert testParser123.flatMap(optional(ch('1'))).tokensToString() == "1"
+    assert testParser123.flatMap(optional(ch('2'))).tokensToString() == ""