diff --git a/vignettes/deviations.Rmd b/vignettes/deviations.Rmd
index 48c11d9..612a0cb 100644
--- a/vignettes/deviations.Rmd
+++ b/vignettes/deviations.Rmd
@@ -1,6 +1,8 @@
 ---
 title: "Deviations from Excel defaults"
-output: rmarkdown::html_vignette
+output:
+  rmarkdown::html_vignette:
+    fig_caption: false
 vignette: >
   %\VignetteIndexEntry{Deviations from Excel defaults}
   %\VignetteEngine{knitr::rmarkdown}
@@ -76,7 +78,7 @@ spc_data %>%
 
 **Over-riding to replicate "Making Data Count" Excel output:**
 
-```{r, fig-alt="An SPC chart labelled Data on the y-axis, with dates from 22 March 2021 to 8 April 2021, at 1-day intervals, on the x-axis. From left to right the line shows four grey common cause points followed by a single blue special cause improvement point followed by a further 12 grey common cause points. A caption reports the upper process limit as 4.6, the mean as 1.94 and the lower process limit as -0.72."}
+```{r, fig.cap="An SPC chart labelled Data on the y-axis, with dates from 22 March 2021 to 8 April 2021, at 1-day intervals, on the x-axis. From left to right the line shows four grey common cause points followed by a single blue special cause improvement point followed by a further 12 grey common cause points. A caption reports the upper process limit as 4.6, the mean as 1.94 and the lower process limit as -0.72."}
 # setting screen_outliers = FALSE produces the same output as Excel
 spc_data <- ptd_spc(df, value_field = data, date_field = date, screen_outliers = FALSE)
 spc_data %>%