diff --git a/include/tidy.h b/include/tidy.h
index bca1463..8a30d9f 100755
--- a/include/tidy.h
+++ b/include/tidy.h
@@ -666,7 +666,7 @@ TIDY_EXPORT int TIDY_CALL     tidySetErrorSink( TidyDoc tdoc, TidyOutputSink* si
 /** Callback to track the progress of the pretting printing process.
 **
 */
-typedef Bool (TIDY_CALL *TidyPPProgress)( TidyDoc tdoc, uint line, uint col, uint destLine );
+typedef void (TIDY_CALL *TidyPPProgress)( TidyDoc tdoc, uint line, uint col, uint destLine );
 
 TIDY_EXPORT Bool TIDY_CALL   tidySetPrettyPrinterCallback( TidyDoc tdoc,
                                                   TidyPPProgress callback );