diff --git a/README.md b/README.md
index bc512f5..73f0ad8 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,7 @@ Defines how the cache is stored and restored. Can be any string (see [Customizab
 
 Very basic local filesystem backend.
 
-The `BUILDKITE_PLUGIN_FS_CACHE_FOLDER` environment variable defines where the copies are  (default: `/var/cache/buildkite`). If you don't change it, you will need to make sure that the folder exists and `buildkite-agent` has the propper permissions, otherwise the plugin will fail. 
+The `BUILDKITE_PLUGIN_FS_CACHE_FOLDER` environment variable defines where the copies are  (default: `/var/cache/buildkite`). If you don't change it, you will need to make sure that the folder exists and `buildkite-agent` has the propper permissions, otherwise the plugin will fail.
 
 **IMPORTANT**: the `fs` backend just copies files to a different location in the current agent, as it is not a shared or external resource, its caching possibilities are quite limited.
 
@@ -59,6 +59,7 @@ Store things in an S3 bucket. You need to make sure that the `aws` command is av
 You also need the agent to have access to the following defined environment variables:
 * `BUILDKITE_PLUGIN_S3_CACHE_BUCKET`: the bucket to use (backend will fail if not defined)
 * `BUILDKITE_PLUGIN_S3_CACHE_PREFIX`: optional prefix to use for the cache within the bucket
+* `BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT`: optional S3 custom endpoint to use
 
 Setting the `BUILDKITE_PLUGIN_S3_CACHE_ONLY_SHOW_ERRORS` environment variable will reduce logging of file operations towards S3.
 
@@ -91,7 +92,7 @@ When restoring from cache, **all levels, in the described order, up to the one s
 
 One of the greatest flexibilities of this plugin is its flexible backend architecture. You can provide whatever value you want for the `backend` option of this plugin (`X` for example) as long as there is an executable script accessible to the agent named `cache_X` that respects the following execution protocol:
 
-* `cache_X exists $KEY` 
+* `cache_X exists $KEY`
 
 Should exit successfully (0 return code) if any previous call to this very same plugin was made with `cache_x save $KEY`. Any other exit code will mean that there is no valid cache and will be ignored.
 
@@ -122,7 +123,7 @@ You can always have more complicated logic by using the plugin multiple times wi
 ```yaml
 steps:
   - label: ':nodejs: Install dependencies'
-    command: npm ci 
+    command: npm ci
     plugins:
       - cache#v0.5.0:
           manifest: package-lock.json
diff --git a/backends/cache_s3 b/backends/cache_s3
index 6642af6..3bde451 100755
--- a/backends/cache_s3
+++ b/backends/cache_s3
@@ -18,13 +18,30 @@ s3_sync() {
   local to="$2"
 
   aws_cmd=(aws s3 sync)
+
   if [ -n "${BUILDKITE_PLUGIN_S3_CACHE_ONLY_SHOW_ERRORS}" ]; then
     aws_cmd+=(--only-show-errors)
   fi
 
+  if [ -n "${BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT}" ]; then
+    aws_cmd+=(--endpoint-url "${BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT}")
+  fi
+
   "${aws_cmd[@]}" "${from}" "${to}"
 }
 
+s3_listobjects() {
+  local prefix="$1"
+
+  aws_cmd=(aws s3api list-objects-v2 --bucket "${BUILDKITE_PLUGIN_S3_CACHE_BUCKET}" --prefix "$(build_key "${prefix}")" --max-items 1)
+
+  if [ -n "${BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT}" ]; then
+    aws_cmd+=(--endpoint-url "${BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT}")
+  fi
+
+  "${aws_cmd[@]}"
+}
+
 restore_cache() {
   local from="$1"
   local to="$2"
@@ -39,7 +56,7 @@ save_cache() {
 
 exists_cache() {
   if [ -z "$1" ]; then exit 1; fi
-  [ -n "$(aws s3api list-objects-v2 --bucket "${BUILDKITE_PLUGIN_S3_CACHE_BUCKET}" --prefix "$(build_key "$1")" --max-items 1)" ]
+  [ -n "$(s3_listobjects "$1")" ]
 }
 
 OPCODE="$1"
diff --git a/tests/cache_s3.bats b/tests/cache_s3.bats
index 5866e7f..67268e6 100644
--- a/tests/cache_s3.bats
+++ b/tests/cache_s3.bats
@@ -91,6 +91,52 @@ setup() {
   unstub aws
 }
 
+@test 'Endpoint URL flag passed when environment is set' {
+  export BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT=https://s3.somewhere.com
+
+  stub aws \
+    's3 sync --endpoint-url https://s3.somewhere.com \* \* : echo ' \
+    's3 sync --endpoint-url https://s3.somewhere.com \* \* : echo ' \
+    's3api list-objects-v2 --bucket \* --prefix \* --max-items 1 --endpoint-url https://s3.somewhere.com : echo exists' \
+    's3 sync \* \* : echo ' \
+    's3 sync \* \* : echo ' \
+    's3api list-objects-v2 --bucket \* --prefix \* --max-items 1 : echo exists'
+
+  run "${PWD}/backends/cache_s3" save from to
+
+  assert_success
+  assert_output ''
+
+  run "${PWD}/backends/cache_s3" get from to
+
+  assert_success
+  assert_output ''
+
+  run "${PWD}/backends/cache_s3" exists to
+
+  assert_success
+  assert_output ''
+
+  unset BUILDKITE_PLUGIN_S3_CACHE_ENDPOINT
+
+  run "${PWD}/backends/cache_s3" save from to
+
+  assert_success
+  assert_output ''
+
+  run "${PWD}/backends/cache_s3" get from to
+
+  assert_success
+  assert_output ''
+
+  run "${PWD}/backends/cache_s3" exists to
+
+  assert_success
+  assert_output ''
+
+  unstub aws
+}
+
 @test 'File exists and can be restored after save' {
   touch "${BATS_TEST_TMPDIR}/new-file"
   mkdir "${BATS_TEST_TMPDIR}/s3-cache"