diff --git a/Dockerfile b/Dockerfile
index 8a676c7..b85a8a0 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -2,10 +2,11 @@ FROM ghcr.io/ropensci-review-tools/pkgcheck:latest
 LABEL maintainer="Jacob Wujciak-Jens <jacob@wujciak.de>"
 
 ENV NOT_CRAN "true"
+ENV CI "ropensci"
 
 COPY R/check.R /check.R
 COPY R/install.R /install.R
 
 RUN ["Rscript", "/install.R"]
 
-ENTRYPOINT [ "Rscript", "/check.R" ]
\ No newline at end of file
+ENTRYPOINT [ "Rscript", "/check.R" ]
diff --git a/README.md b/README.md
index 298f4f9..a444323 100644
--- a/README.md
+++ b/README.md
@@ -52,6 +52,15 @@ jobs:
 
 There are also several parameters which can be used to modify the workflow, as described in the following section.
 
+### Environment variables
+
+This action runs with one environment variable of `CI = "ropensci"`. This
+enables
+[`testthat::skip_on_ci()`](https://testthat.r-lib.org/reference/skip.html),
+which skips tests if a variable named "CI" is set, regardless of value.
+Alternately, tests can be fine-tuned to skip within `pkgcheck` by setting
+`testthat::skip_if(Sys.getenv("CI") == "ropensci")`.
+
 ### Workflow parameters
 
 The [`yaml` workflow