diff --git a/NEWS.md b/NEWS.md
index ad7f0f631..0436668f1 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # devtools 2.0.1.9000 - Development
 
+* `check()` now replaces existing environment variables rather than appending
+  them (#1914).
+
 # devtools 2.0.1
 
 This is a minor release mainly fixing bugs which snuck through in the devtools
diff --git a/R/check.R b/R/check.R
index 08a746477..50a83fc4a 100644
--- a/R/check.R
+++ b/R/check.R
@@ -191,7 +191,7 @@ check_built <- function(path = NULL, cran = TRUE,
     show_env_vars(env_vars, trailing = FALSE)
   }
 
-  withr::with_envvar(env_vars, action = "prefix", {
+  withr::with_envvar(env_vars, action = "replace", {
     rcmdcheck::rcmdcheck(path,
       quiet = quiet, args = args,
       check_dir = check_dir, error_on = error_on