diff --git a/dashboard/src/components/BackupSiteContentDialog.vue b/dashboard/src/components/BackupSiteContentDialog.vue
index fe1bfb197..76f3e2eea 100644
--- a/dashboard/src/components/BackupSiteContentDialog.vue
+++ b/dashboard/src/components/BackupSiteContentDialog.vue
@@ -35,8 +35,20 @@ async function onSubmit() {
   if (includeExclude.value === 'everything') {
     contents = null;
   } else if (includeExclude.value === 'exclude') {
+    if (contentExclude.value.length === 0) {
+      formError.value.includeExclude = 'Exclude at least one content item or select Everything';
+      busy.value = false;
+      return;
+    }
+
     contents = { exclude: contentExclude.value };
-  } else if (includeExclude.value === 'include' && contentInclude.value.length) {
+  } else if (includeExclude.value === 'include') {
+    if (contentInclude.value.length === 0) {
+      formError.value.includeExclude = 'Include at least one content item';
+      busy.value = false;
+      return;
+    }
+
     contents = { include: contentInclude.value };
   }
 
@@ -121,12 +133,13 @@ defineExpose({
             <FormGroup>
               <label>{{  $t('backups.configureBackupStorage.backupContents.title') }}</label>
               <div>{{ $t('backups.configureBackupStorage.backupContents.description') }}</div>
+              <div class="error-label" v-if="formError.includeExclude">{{ formError.includeExclude }}</div>
               <div style="padding-top: 10px">
                 <Radiobutton v-model="includeExclude" value="everything" :label="$t('backups.configureBackupStorage.backupContents.everything')"/>
                 <Radiobutton v-model="includeExclude" value="exclude" :label="$t('backups.configureBackupStorage.backupContents.excludeSelected')"/>
-                <MultiSelect v-model="contentExclude" v-if="includeExclude === 'exclude'" :options="contentOptions" :search-threshold="10" option-key="id" style="margin: 6px 0 6px 25px;"/>
+                <MultiSelect v-model="contentExclude" v-if="includeExclude === 'exclude'" required :options="contentOptions" :search-threshold="10" option-key="id" style="margin: 6px 0 6px 25px;"/>
                 <Radiobutton v-model="includeExclude" value="include" :label="$t('backups.configureBackupStorage.backupContents.includeOnlySelected')"/>
-                <MultiSelect v-model="contentInclude" v-if="includeExclude === 'include'" :options="contentOptions" :search-threshold="10" option-key="id" style="margin: 6px 0 6px 25px;"/>
+                <MultiSelect v-model="contentInclude" v-if="includeExclude === 'include'" required :options="contentOptions" :search-threshold="10" option-key="id" style="margin: 6px 0 6px 25px;"/>
               </div>
             </FormGroup>