diff --git a/vignettes/landscapes.Rmd b/vignettes/landscapes.Rmd
index 70d7a587..b9e23050 100644
--- a/vignettes/landscapes.Rmd
+++ b/vignettes/landscapes.Rmd
@@ -115,9 +115,9 @@ A variety of R add-on packages facilitate three-dimensional plots.
 
 ```{r plot-3d, message = FALSE}
 if (requireNamespace("plotly", quietly = TRUE)) {
-  library("plotly", quietly = TRUE)
-  fig <- plot_ly(x = x, y = y, z = z)
-  fig <- fig %>% add_surface()
+  # Don't attach plotly: it would mask `graphics::layout()` in later vignettes
+  fig <- plotly::plot_ly(x = x, y = y, z = z)
+  fig <- plotly::add_surface(fig)
   fig
 } else {
   print("Run `install.packages('plotly')` to view this output")
diff --git a/vignettes/treespace.Rmd b/vignettes/treespace.Rmd
index 62e2bbec..3c18cdfe 100644
--- a/vignettes/treespace.Rmd
+++ b/vignettes/treespace.Rmd
@@ -293,7 +293,7 @@ plotSeq <- matrix(0, nDim, nDim)
 plotSeq[upper.tri(plotSeq)] <- seq_len(nDim * (nDim - 1) / 2)
 plotSeq <- t(plotSeq[-nDim, -1])
 plotSeq[nDim * 1:3] <- (nDim * (nDim - 1) / 2) + 1:3
-layout(plotSeq)
+graphics::layout(plotSeq)
 par(mar = rep(0.1, 4))
 
 for (i in 2:nDim) for (j in seq_len(i - 1)) {