diff --git a/README.md b/README.md
index e167c9f..c3f2ecc 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,17 @@ curl -fsSL https://git.ccc-rheintal.ch/spacefreak/pbc/raw/branch/master/install.
 This installs the newest tagged version to `/usr/local/bin/pbc`, installs the
 dependencies, and puts an example config at `/etc/pbc/config.example`.
 
+### Installing a specific version
+
+Set `PBC_GIT_TAG` to install that tag instead of the newest one:
+
+```bash
+curl -fsSL https://git.ccc-rheintal.ch/spacefreak/pbc/raw/branch/master/install.sh | sudo PBC_GIT_TAG=v1.0.0 bash
+```
+
+`sudo` drops the environment, so set the variable on the `sudo` command itself (or use
+`sudo -E`), not before `curl`. Any Git ref works, e.g. a branch name for testing.
+
 ### Updating
 
 Run the same command again to update `pbc` itself:
@@ -32,7 +43,7 @@ curl -fsSL https://git.ccc-rheintal.ch/spacefreak/pbc/raw/branch/master/install.
 ```
 
 It fetches the newest tag and overwrites `/usr/local/bin/pbc`. Your `/etc/pbc/config` is
-left untouched.
+left untouched. `PBC_GIT_TAG` works here too, to pin or roll back to a given version.
 
 To update only the `proxmox-backup-client` binary:
 
diff --git a/install.sh b/install.sh
index 6832462..acbfc6b 100755
--- a/install.sh
+++ b/install.sh
@@ -13,7 +13,7 @@ function cleanup_work_dir() {
 function download_files() {
   local path rc
   local query_params=''
-  [ -n "$GIT_TAG" ] && query_params="?ref=$GIT_TAG"
+  [ -n "$PBC_GIT_TAG" ] && query_params="?ref=$PBC_GIT_TAG"
 
   while (( $# > 0 )); do
     path=$1
@@ -26,9 +26,9 @@ function download_files() {
   done
 }
 
-GIT_TAG=$(curl -fsSL "$API_ENDPOINT/tags" | grep -o '{"name":"[^"]*"' | sed 's/^{"name":"//;s/"$//' | grep -E '^v[0-9]+' | sort --version-sort | tail -n 1)
-if [ -n "$GIT_TAG" ]; then
-  echo "Info: installing pbc version $GIT_TAG"
+[ -z "$PBC_GIT_TAG" ] && PBC_GIT_TAG=$(curl -fsSL "$API_ENDPOINT/tags" | grep -o '{"name":"[^"]*"' | sed 's/^{"name":"//;s/"$//' | grep -E '^v[0-9]+' | sort --version-sort | tail -n 1)
+if [ -n "$PBC_GIT_TAG" ]; then
+  echo "Info: installing pbc version $PBC_GIT_TAG"
 else
   echo "Warning: no Git tag found, installing from repository default branch" >&2
 fi