diff --git a/DESCRIPTION b/DESCRIPTION
index 55bd4638c..3cf53a028 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -106,7 +106,7 @@ Depends:
 Imports:
   base64url,
   digest (>= 0.6.21),
-  igraph,
+  igraph (>= 2.0.0),
   methods,
   parallel,
   rlang (>= 0.2.0),
diff --git a/NAMESPACE b/NAMESPACE
index ac48457b8..d98df8fa0 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -429,6 +429,7 @@ importFrom(igraph,make_empty_graph)
 importFrom(igraph,set_vertex_attr)
 importFrom(igraph,simplify)
 importFrom(igraph,topo_sort)
+importFrom(igraph,union)
 importFrom(igraph,vertex_attr)
 importFrom(methods,new)
 importFrom(methods,setRefClass)
diff --git a/R/create_drake_graph.R b/R/create_drake_graph.R
index 2a5821f31..3b0a42e00 100644
--- a/R/create_drake_graph.R
+++ b/R/create_drake_graph.R
@@ -92,7 +92,7 @@ cdg_transitive_edges <- function(vertex, edges, args) {
 cdg_finalize_graph <- function(edges, targets, args) {
   args$logger$disk("finalize graph edges")
   file_out <- edges$to[edges$from %in% targets & is_encoded_path(edges$to)]
-  to <- union(targets, file_out)
+  to <- base::union(targets, file_out)
   args$logger$disk("create igraph")
   graph <- igraph::graph_from_data_frame(edges)
   args$logger$disk("trim neighborhoods")
diff --git a/R/drake_plan.R b/R/drake_plan.R
index c35cae0d0..22b62211b 100644
--- a/R/drake_plan.R
+++ b/R/drake_plan.R
@@ -358,7 +358,7 @@ drake_bind_rows <- function(...) {
   flatten_df_list(args, df_env = df_env)
   dfs <- df_env$dfs
   cols <- lapply(dfs, colnames)
-  cols <- Reduce(f = union, x = cols)
+  cols <- Reduce(f = base::union, x = cols)
   dfs <- lapply(dfs, fill_cols, cols = cols)
   do.call(rbind, dfs)
 }
diff --git a/R/dynamic.R b/R/dynamic.R
index 38c3e900d..1430a2573 100644
--- a/R/dynamic.R
+++ b/R/dynamic.R
@@ -297,7 +297,7 @@ register_in_graph <- function(target, subtargets, config) {
     name = "imported",
     value = FALSE
   )
-  config$envir_graph$graph <- igraph::graph.union(
+  config$envir_graph$graph <- igraph::union(
     config$envir_graph$graph,
     subgraph
   )
diff --git a/R/make.R b/R/make.R
index 621f4a4ed..561955475 100644
--- a/R/make.R
+++ b/R/make.R
@@ -53,7 +53,7 @@
 #' For each target that is still problematic  (e.g.
 #' `https://github.com/rstudio/gt/issues/297`)
 #' you can safely run the command in its own special `callr::r()` process.
-#' Example: `https://github.com/rstudio/gt/issues/297#issuecomment-497778735`. # nolin
+#' Example: `https://github.com/rstudio/gt/issues/297#issuecomment-497778735`. # nolint
 #' @section Cache locking:
 #' When `make()` runs, it locks the cache so other processes cannot modify it.
 #' Same goes for [outdated()], [vis_drake_graph()], and similar functions
@@ -397,7 +397,7 @@ drake_set_session_info <- function(
 #' })
 #' }
 do_prework <- function(config, verbose_packages) {
-  for (package in union(c("methods", "drake"), config$packages)) {
+  for (package in base::union(c("methods", "drake"), config$packages)) {
     expr <- as.call(c(
       quote(require),
       package = package,
diff --git a/R/package.R b/R/package.R
index d35180005..1a8c7059d 100644
--- a/R/package.R
+++ b/R/package.R
@@ -48,7 +48,7 @@
 #' @importFrom igraph adjacent_vertices as_ids components delete_vertices
 #'   degree gorder graph_from_adjacency_matrix igraph_opt igraph_options
 #'   induced_subgraph is_dag make_empty_graph make_ego_graph set_vertex_attr
-#'   simplify topo_sort V vertex_attr
+#'   simplify topo_sort union V vertex_attr
 #' @importFrom methods new setRefClass
 #' @importFrom parallel mclapply
 #' @importFrom rlang dots_list enquo eval_tidy expr quo_squash quos trace_back
diff --git a/R/predict_runtime.R b/R/predict_runtime.R
index 4ed99eb39..3bc783d11 100644
--- a/R/predict_runtime.R
+++ b/R/predict_runtime.R
@@ -299,7 +299,7 @@ register_subtargets_graph2 <- function(target, subtargets, config) {
     name = "imported",
     value = FALSE
   )
-  config$graph <- igraph::graph.union(config$graph, subgraph)
+  config$graph <- igraph::union(config$graph, subgraph)
   config
 }
 
diff --git a/man/make.Rd b/man/make.Rd
index 2a293260f..6b48c8d5e 100644
--- a/man/make.Rd
+++ b/man/make.Rd
@@ -53,7 +53,7 @@ make(
   memory_strategy = "speed",
   layout = NULL,
   spec = NULL,
-  lock_envir = TRUE,
+  lock_envir = NULL,
   history = TRUE,
   recover = FALSE,
   recoverable = TRUE,
@@ -606,14 +606,7 @@ during \code{make()} itself.
 For each target that is still problematic  (e.g.
 \verb{https://github.com/rstudio/gt/issues/297})
 you can safely run the command in its own special \code{callr::r()} process.
-Example: \verb{https://github.com/rstudio/gt/issues/297#issuecomment-497778735}. # nolint
-
-If that fails, you can run \code{make(plan, lock_envir = FALSE)}
-to suppress environment-locking for all targets.
-However, this is not usually recommended.
-There are legitimate use cases for \code{lock_envir = FALSE}
-(example: \verb{https://books.ropensci.org/drake/hpc.html#parallel-computing-within-targets}) # nolint
-but most workflows should stick with the default \code{lock_envir = TRUE}.
+Example: \verb{https://github.com/rstudio/gt/issues/297#issuecomment-497778735}. # nolin
 }
 
 \section{Cache locking}{
diff --git a/tests/testthat/test-1-interactive.R b/tests/testthat/test-1-interactive.R
index 25eee4026..fcabf08c1 100644
--- a/tests/testthat/test-1-interactive.R
+++ b/tests/testthat/test-1-interactive.R
@@ -276,22 +276,6 @@ test_with_dir("clustermq error messages get back to main", {
 })
 }
 
-if (FALSE) {
-test_with_dir("forks + lock_envir = informative warning msg", {
-  skip_on_cran()
-  # Don't run this test for real because (1) we would have to add
-  # furrr to "Suggests" and (2) at some point, base R may be patched
-  # so forking in the parallel package does not give this warning anyway.
-  # Also, it needs to run outside the RStudio IDE so we can fork processes.
-  regexp <- "workaround"
-  plan <- drake_plan(x = parallel::mclapply(1:2, identity, mc.cores = 2))
-  expect_warning(
-    make(plan, envir = globalenv(), lock_envir = TRUE),
-    regexp = regexp
-  )
-})
-}
-
 if (FALSE) {
 test_with_dir("clean() in interactive mode", {
   skip_on_cran()
diff --git a/tests/testthat/test-8-cache.R b/tests/testthat/test-8-cache.R
index 4e69a2a4e..55f2248e3 100644
--- a/tests/testthat/test-8-cache.R
+++ b/tests/testthat/test-8-cache.R
@@ -817,7 +817,7 @@ test_with_dir("cache log files, gc, and make()", {
 
 test_with_dir("try_build() does not need to access cache", {
   skip_on_cran() # CRAN gets essential tests only (check time limits).
-  config <- drake_config(drake_plan(x = 1), lock_envir = FALSE)
+  config <- drake_config(drake_plan(x = 1))
   meta <- drake_meta_(target = "x", config = config)
   config$cache <- config$settings$cache_log_file <- NULL
   build <- try_build(target = "x", meta = meta, config = config)
diff --git a/tests/testthat/test-9-clustermq.R b/tests/testthat/test-9-clustermq.R
index 448c1264e..80f8539c1 100644
--- a/tests/testthat/test-9-clustermq.R
+++ b/tests/testthat/test-9-clustermq.R
@@ -45,8 +45,7 @@ test_with_dir("clustermq parallelism", {
       caching = caching,
       envir = e,
       verbose = 1L,
-      garbage_collection = TRUE,
-      lock_envir = TRUE
+      garbage_collection = TRUE
     )
     expect_equal(outdated_impl(config), character(0))
     make(
@@ -55,8 +54,7 @@ test_with_dir("clustermq parallelism", {
       jobs = jobs,
       caching = caching,
       envir = e,
-      verbose = 1L,
-      lock_envir = TRUE
+      verbose = 1L
     )
     expect_equal(justbuilt(config), character(0))
     e$my_plan$command[[2]] <- as.call(
@@ -68,8 +66,7 @@ test_with_dir("clustermq parallelism", {
       jobs = jobs,
       caching = caching,
       envir = e,
-      verbose = 1L,
-      lock_envir = TRUE
+      verbose = 1L
     )
     expect_equal(justbuilt(config), "small")
     clean(small, cache = config$cache)
@@ -79,8 +76,7 @@ test_with_dir("clustermq parallelism", {
       jobs = jobs,
       caching = caching,
       envir = e,
-      verbose = 1L,
-      lock_envir = TRUE
+      verbose = 1L
     )
     expect_equal(justbuilt(config), "small")
   }
@@ -172,8 +168,7 @@ test_with_dir("Start off with non-HPC targets, then go to HPC targets.", {
     jobs = jobs,
     envir = e,
     verbose = 1L,
-    garbage_collection = TRUE,
-    lock_envir = TRUE
+    garbage_collection = TRUE
   )
   config <- drake_config(e$my_plan, envir = e)
   expect_equal(sort(justbuilt(config)), sort(e$my_plan$target))
diff --git a/tests/testthat/test-9-future.R b/tests/testthat/test-9-future.R
index d2cb59cb1..5e6a6be8d 100644
--- a/tests/testthat/test-9-future.R
+++ b/tests/testthat/test-9-future.R
@@ -30,8 +30,7 @@ test_with_dir("future package functionality", {
       caching = caching[i],
       jobs = 1,
       verbose = 0L,
-      session_info = FALSE,
-      lock_envir = TRUE
+      session_info = FALSE
     )
     config <- drake_config(
       e$my_plan,
@@ -40,8 +39,7 @@ test_with_dir("future package functionality", {
       caching = caching[i],
       jobs = 1,
       verbose = 0L,
-      session_info = FALSE,
-      lock_envir = TRUE
+      session_info = FALSE
     )
     expect_equal(
       outdated_impl(config),
@@ -57,8 +55,7 @@ test_with_dir("future package functionality", {
       caching = caching[i],
       jobs = 1,
       verbose = 0L,
-      session_info = FALSE,
-      lock_envir = TRUE
+      session_info = FALSE
     )
     expect_equal(justbuilt(config), "small")
   }
@@ -72,8 +69,7 @@ test_with_dir("future package functionality", {
       caching = caching[i],
       jobs = 1,
       verbose = 0L,
-      session_info = FALSE,
-      lock_envir = TRUE
+      session_info = FALSE
     )
     config <- drake_config(
       e$my_plan,
@@ -82,8 +78,7 @@ test_with_dir("future package functionality", {
       caching = caching[i],
       jobs = 1,
       verbose = 0L,
-      session_info = FALSE,
-      lock_envir = TRUE
+      session_info = FALSE
     )
     nobuild(config)
   }