diff --git a/src/FsYacc.Core/fsyaccdriver.fs b/src/FsYacc.Core/fsyaccdriver.fs
index 5ca3076..b2cda9c 100644
--- a/src/FsYacc.Core/fsyaccdriver.fs
+++ b/src/FsYacc.Core/fsyaccdriver.fs
@@ -647,7 +647,7 @@ let writeSpecToFile (generatorState: GeneratorState) (spec: ParserSpec) (compile
 
     for id, startState in List.zip spec.StartSymbols compiledSpec.startStates do
         if not (types.ContainsKey id) then
-            failwith ("a %type declaration is required for for start token " + id)
+            failwith ("a %type declaration is required for start token " + id)
 
         let ty = types.[id] in
         writer.WriteLine "let %s lexer lexbuf : %s =" id ty