diff --git a/vignettes/MetaboAnnotation.Rmd b/vignettes/MetaboAnnotation.Rmd
index cec5c12..f186d1b 100644
--- a/vignettes/MetaboAnnotation.Rmd
+++ b/vignettes/MetaboAnnotation.Rmd
@@ -493,7 +493,8 @@ replace the absolute spectra intensities with intensities relative to the
 maximum intensity of each spectrum.
 
 ```{r}
-scale_int <- function(x) {
+
+scale_int <- function(x,...) {
     x[, "intensity"] <- x[, "intensity"] / max(x[, "intensity"], na.rm = TRUE)
     x
 }