diff --git a/infra/deploy.ps1 b/infra/deploy.ps1
index 42cbc2b53..12656e9a9 100644
--- a/infra/deploy.ps1
+++ b/infra/deploy.ps1
@@ -45,7 +45,7 @@
     SSW.Rules.Content branch the Rules Chat index job reads. Default: main.
 
 .PARAMETER RulesChatIndexImageTag
-    Tag of the rules-chat-index image the index job runs. Default: the same tag as the site image.
+    Tag of the rules-chat-index image the index job runs. Only the deploy workflow builds and pushes this image.
 
 .PARAMETER RulesChatAlertEmail
     Optional email address for index job failure and staleness alerts.
@@ -87,8 +87,8 @@ param(
     [Parameter(Mandatory = $false)]
     [string]$RulesChatContentBranch = 'main',
 
-    [Parameter(Mandatory = $false)]
-    [string]$RulesChatIndexImageTag = '',
+    [Parameter(Mandatory = $true)]
+    [string]$RulesChatIndexImageTag,
 
     [Parameter(Mandatory = $false)]
     [string]$RulesChatAlertEmail = '',
@@ -456,9 +456,7 @@ $azArgs += '--parameters', "rulesChatFoundryName=$RulesChatFoundryName"
 $azArgs += '--parameters', "rulesChatContainerAppsEnvironmentName=$RulesChatContainerAppsEnvironmentName"
 $azArgs += '--parameters', "rulesChatIndexJobName=$RulesChatIndexJobName"
 $azArgs += '--parameters', "rulesChatContentBranch=$RulesChatContentBranch"
-if ($RulesChatIndexImageTag) {
-    $azArgs += '--parameters', "rulesChatIndexImageTag=$RulesChatIndexImageTag"
-}
+$azArgs += '--parameters', "rulesChatIndexImageTag=$RulesChatIndexImageTag"
 if ($RulesChatAlertEmail) {
     $azArgs += '--parameters', "rulesChatAlertEmail=$RulesChatAlertEmail"
 }
diff --git a/infra/main.bicep b/infra/main.bicep
index 2f6866800..ad35c703f 100644
--- a/infra/main.bicep
+++ b/infra/main.bicep
@@ -117,8 +117,8 @@ param rulesChatContainerAppsEnvironmentName string
 @description('Name of the Container Apps job that indexes the rules (32 characters at most)')
 param rulesChatIndexJobName string
 
-@description('Tag of the index job image. A tag unique to each build, so the job never runs an older image cached under the same tag.')
-param rulesChatIndexImageTag string = imageTag
+@description('Tag of the index job image. A tag unique to each build, so the job never runs an older image cached under the same tag. Only the deploy workflow builds and pushes this image.')
+param rulesChatIndexImageTag string
 
 @description('SSW.Rules.Content branch the index job reads, matching the content this environment shows')
 param rulesChatContentBranch string = 'main'