diff --git a/R/plotDists.R b/R/plotDists.R
index 643f92a..bdf0c6a 100644
--- a/R/plotDists.R
+++ b/R/plotDists.R
@@ -33,19 +33,19 @@ NULL
 plotDist_ <- function(support, hseq, dist, params) {
 
   discretes <- c('Poisson')
-
-  ribbon_or_bar <- ggplot2::geom_ribbon(ggplot2::aes(ymax = .data$hseq),
-                                        ymin = 0,
-                                        size = 2,
-                                        color = I("lightblue"),
-                                        fill = "lightgreen",
-                                        alpha = .25)
+  
+  args <- list(size = 2, color = I("lightblue"), fill = "lightgreen", alpha = .25)
+  if (packageVersion("ggplot2") > "3.4.0") {
+    names(args)[1] <- "linewidth"
+  }
+  
+  ribbon_or_bar <- do.call(
+    ggplot2::geom_ribbon, 
+    c(list(mapping = ggplot2::aes(ymax = .data$hseq), ymin = 0), args)
+  )
 
   if(dist %in% discretes) {
-    ribbon_or_bar <- ggplot2::geom_col(size = 2,
-                                       color = I("lightblue"),
-                                       fill = "lightgreen",
-                                       alpha = .25)
+    ribbon_or_bar <- do.call(ggplot2::geom_col, args)
     notEmpty <- hseq != 0
     support <- support[notEmpty]
     hseq <- hseq[notEmpty]
@@ -232,11 +232,17 @@ plotNormalInvGamma <- function(mu, lambda, alpha, beta) {
   inputs <- expand.grid(x, sig_sq)
   out <- dNormalInverseGamma(inputs$Var1, inputs$Var2, mu, lambda, alpha, beta)
   dat <- data.frame(x = inputs$Var1, sig_sq = inputs$Var2, res = out)
+  
+  level_mapping <- if (packageVersion("ggplot2") > "3.4.0") {
+    ggplot2::aes(fill = ggplot2::after_stat(.data[["level"]]))
+  } else {
+    ggplot2::aes_string(fill = "..level..")
+  }
 
-  p <- ggplot2::ggplot(dat, ggplot2::aes_string('x', 'sig_sq', z = 'res')) +
+  p <- ggplot2::ggplot(dat, ggplot2::aes(.data[['x']], .data[['sig_sq']], z = .data[['res']])) +
     ggplot2::ggtitle(paste0('Normal Inverse Gamma PDF for ',
                             paste0(c(mu, lambda, alpha, beta), collapse = ", "))) +
-    ggplot2::stat_contour(ggplot2::aes_string(fill = '..level..'), geom = "polygon", bins = 10) +
+    ggplot2::stat_contour(level_mapping, geom = "polygon", bins = 10) +
     ggplot2::scale_fill_continuous(name = 'Probability Density', position = 'bottom') +
     theme_bayesAB() +
     ggplot2::theme(legend.position = 'bottom')
diff --git a/tests/testthat/test-dists.R b/tests/testthat/test-dists.R
index 2fe6a37..e753ec5 100644
--- a/tests/testthat/test-dists.R
+++ b/tests/testthat/test-dists.R
@@ -19,18 +19,23 @@ test_that("Closure madness", {
 })
 
 test_that("Success", {
-
-  expect_equal(plotPoisson(1)$labels$y, 'PDF')
-  expect_equal(plotPareto(1, 1)$labels$y, 'PDF')
-  expect_equal(plotNormal(1, 1)$labels$y, 'PDF')
-  expect_equal(plotGamma(1, 1)$labels$y, 'PDF')
-  expect_equal(plotBeta(1, 1)$labels$y, 'PDF')
-  expect_equal(plotInvGamma(1, 1)$labels$y, 'PDF')
-  expect_equal(plotLogNormal(1, 1)$labels$y, 'PDF')
+  
+  get_labs <- function(x) x$labels
+  if ("get_labs" %in% getNamespaceExports("ggplot2")) {
+    get_labs <- ggplot2::get_labs
+  }
+
+  expect_equal(get_labs(plotPoisson(1))$y, 'PDF')
+  expect_equal(get_labs(plotPareto(1, 1))$y, 'PDF')
+  expect_equal(get_labs(plotNormal(1, 1))$y, 'PDF')
+  expect_equal(get_labs(plotGamma(1, 1))$y, 'PDF')
+  expect_equal(get_labs(plotBeta(1, 1))$y, 'PDF')
+  expect_equal(get_labs(plotInvGamma(1, 1))$y, 'PDF')
+  expect_equal(get_labs(plotLogNormal(1, 1))$y, 'PDF')
   expect_equal(qinvgamma(1 - (.Machine$double.eps) / 2, 2, 2), Inf)
   expect_equal(dpareto(c(0, 1, 2), 1, 1), c(0, 0, .25))
   expect_equal(dpareto(c(5, 15), 20, 3), c(0, 0))
   expect_equal(max(plotNormalInvGamma(3, 100, 51, 216)$data$sig_sq), qgamma(.99, 51, 216) * 100)
-  expect_equal(plotNormalInvGamma(3, 1, 1, 1)$labels$y, 'sig_sq')
+  expect_equal(get_labs(plotNormalInvGamma(3, 1, 1, 1))$y, 'sig_sq')
 
 })