diff --git a/CHANGELOG.md b/CHANGELOG.md
index 53171c7c1c..4b9113b73a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -56,6 +56,7 @@ BUG FIXES:
 * Fix VM actions where Workspace shared storage doesn't allow shared key access ([#4222](https://github.com/microsoft/AzureTRE/issues/4222))
 * Fix public exposure in Guacamole service ([[#4199](https://github.com/microsoft/AzureTRE/issues/4199)])
 * Fix Azure ML network tags to use name rather than ID ([[#4151](https://github.com/microsoft/AzureTRE/issues/4151)])
+* Windows R version must be 4.1.2 otherwise post install script doesn't update package mirror URL ([#4288](https://github.com/microsoft/AzureTRE/issues/4288))
 * Recreate tre_output.json if empty. ([[#4292](https://github.com/microsoft/AzureTRE/issues/4292)])
 
 COMPONENTS:
diff --git a/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/porter.yaml b/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/porter.yaml
index 8587988668..0f727c688b 100644
--- a/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/porter.yaml
+++ b/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/porter.yaml
@@ -1,7 +1,7 @@
 ---
 schemaVersion: 1.0.0
 name: tre-service-guacamole-windowsvm
-version: 1.2.4
+version: 1.2.5
 description: "An Azure TRE User Resource Template for Guacamole (Windows 10)"
 dockerfile: Dockerfile.tmpl
 registry: azuretre
diff --git a/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/terraform/vm_config.ps1 b/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/terraform/vm_config.ps1
index f2604f7a3b..343ac0e33c 100644
--- a/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/terraform/vm_config.ps1
+++ b/templates/workspace_services/guacamole/user_resources/guacamole-azure-windowsvm/terraform/vm_config.ps1
@@ -44,9 +44,6 @@ $DaemonConfig = @"
 $DaemonConfig | Out-File -Encoding Ascii ( New-Item -Path $env:ProgramData\docker\config\daemon.json -Force )
 
 # R config
-# $RconfigFilePathWindows = C:\Progra~1\R\4.1.2\etc\Rprofile.site
-#Add-Content $RconfigFilePathWindows "local({`n    r <- getOption(`"repos`")`n    r[`"Nexus`"] <- `"${nexus_proxy_url}/repository/r-proxy/`"`n    options(repos = r)`n})"
-# echo "local({`n    r <- getOption(`"repos`")`n    r[`"Nexus`"] <- `"${nexus_proxy_url}/repository/r-proxy/`"`n    options(repos = r)`n})" > $RconfigFilePathWindows
 $RConfig = @"
 local({
     r <- getOption("repos")
@@ -54,5 +51,11 @@ local({
     options(repos = r)
 })
 "@
-$RConfig | Out-File -Encoding Ascii ( New-Item -Path $Env:ProgramFiles\R\R-4.1.2\etc\Rprofile.site -Force )
 
+$RBasePath = "$Env:ProgramFiles\R"
+$RVersions = Get-ChildItem -Path $RBasePath -Directory | Where-Object { $_.Name -like "R-*" }
+
+foreach ($RVersion in $RVersions) {
+    $ConfigPath = Join-Path -Path $RVersion.FullName -ChildPath "etc\Rprofile.site"
+    $RConfig | Out-File -Encoding Ascii (New-Item -Path $ConfigPath -Force)
+}