diff --git a/vignettes/BasicREDCapROperations.Rmd b/vignettes/BasicREDCapROperations.Rmd
index ebeeea30..8996abed 100644
--- a/vignettes/BasicREDCapROperations.Rmd
+++ b/vignettes/BasicREDCapROperations.Rmd
@@ -18,6 +18,7 @@ The functions [`redcap_read()`](https://ouhscbbmc.github.io/REDCapR/reference/re
 #| echo = FALSE, results = 'hide'
 
 report_render_start_time <- Sys.time()
+report_render_duration_in_seconds <- -999 # In case the vignette isn't evaluated (on CRAN)
 
 library(knitr)
 library(magrittr)
@@ -165,7 +166,7 @@ if (requireNamespace("sessioninfo", quietly = TRUE)) {
 </details>
 
 ```{r session-duration, echo=FALSE}
-report_render_duration <- round(as.numeric(difftime(Sys.time(), report_render_start_time, units = "secs")))
+report_render_duration_in_seconds <- round(as.numeric(difftime(Sys.time(), report_render_start_time, units = "secs")))
 ```
 
-Report rendered by `r Sys.info()["user"]` at `r strftime(Sys.time(), "%Y-%m-%d, %H:%M %z")` in `r report_render_duration` seconds.
+Report rendered by `r Sys.info()["user"]` at `r strftime(Sys.time(), "%Y-%m-%d, %H:%M %z")` in `r report_render_duration_in_seconds` seconds.
diff --git a/vignettes/advanced-redcapr-operations.Rmd b/vignettes/advanced-redcapr-operations.Rmd
index 51ec1120..954382d8 100644
--- a/vignettes/advanced-redcapr-operations.Rmd
+++ b/vignettes/advanced-redcapr-operations.Rmd
@@ -15,6 +15,7 @@ This vignette covers the the less-typical uses of [REDCapR](https://github.com/O
 #| results = 'hide'
 
 report_render_start_time <- Sys.time()
+report_render_duration_in_seconds <- -999 # In case the vignette isn't evaluated (on CRAN)
 
 library(knitr)
 library(magrittr)