diff --git a/.github/workflows/check-full.yaml b/.github/workflows/check-full.yaml
index a6455e3..05c10e9 100644
--- a/.github/workflows/check-full.yaml
+++ b/.github/workflows/check-full.yaml
@@ -1,9 +1,3 @@
-# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
-# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
-#
-# NOTE: This workflow is overkill for most R packages and
-# check-standard.yaml is likely a better choice.
-# usethis::use_github_action("check-standard") will install it.
 on:
   push:
     branches: [main, master]
@@ -30,13 +24,13 @@ jobs:
           - { os: windows-latest, r: "release" }
           - { os: windows-latest, r: "oldrel-1" }
 
-          # Use older ubuntu to maximise backward compatibility
           - { os: ubuntu-latest, r: "devel", http-user-agent: "release" }
           - { os: ubuntu-latest, r: "release" }
           - { os: ubuntu-latest, r: "oldrel-1" }
           - { os: ubuntu-latest, r: "oldrel-2" }
           - { os: ubuntu-latest, r: "oldrel-3" }
           - { os: ubuntu-latest, r: "oldrel-4" }
+          - { os: ubuntu-latest, r: "3.6" }
 
     env:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.gitignore b/.gitignore
index 28c38a2..00d43f7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -50,3 +50,4 @@ revdep/library.noindex
 revdep/data.sqlite
 /doc/
 /Meta/
+tests/testthat/Rplots.pdf
diff --git a/DESCRIPTION b/DESCRIPTION
index b23ad42..eb9cb2c 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -31,13 +31,15 @@ VignetteBuilder:
     knitr
 Encoding: UTF-8
 Language: en-US
+Depends: 
+    R (>= 3.6.0)
 Imports:
     ggplot2 (>= 3.5.0)
 Suggests: 
     knitr,
     rmarkdown,
     testthat,
-    vdiffr (>= 1.0.5)
+    vdiffr (>= 1.0.7)
 Roxygen: list(markdown = TRUE, roclets = c("rd", "namespace", "collate"))
 RoxygenNote: 7.3.1
 Config/testthat/edition: 3
diff --git a/tests/testthat/test-geom_signific_strict.R b/tests/testthat/test-geom_signific_strict.R
index 609586c..3116626 100644
--- a/tests/testthat/test-geom_signific_strict.R
+++ b/tests/testthat/test-geom_signific_strict.R
@@ -1,7 +1,5 @@
 test_that("the plotting works - strict test", {
-  # don't run on CRAN; allows ggplot2 people to make changes to internal dataframes
   skip_on_cran()
-  skip_if(getRversion() < "4.0")
 
   library(ggplot2)
 
diff --git a/tests/testthat/test-vdiffr.R b/tests/testthat/test-vdiffr.R
index cbf0a1f..0a78332 100644
--- a/tests/testthat/test-vdiffr.R
+++ b/tests/testthat/test-vdiffr.R
@@ -1,7 +1,6 @@
 test_that("plots are rendered correctly", {
   skip_on_cran()
   skip_if_not_installed("vdiffr")
-  skip_if(getRversion() < "4.1")
   library(ggplot2)
 
   set.seed(123)