diff --git a/Makefile b/Makefile
index c8af5593..41b39142 100644
--- a/Makefile
+++ b/Makefile
@@ -66,6 +66,7 @@ PROMETHEUS_NAMESPACE=gotenberg
 PROMETHEUS_COLLECT_INTERVAL=1s
 PROMETHEUS_DISABLE_ROUTE_LOGGING=false
 PROMETHEUS_DISABLE_COLLECT=false
+WEBHOOK_ENABLE_SYNC_MODE=false
 WEBHOOK_ALLOW_LIST=
 WEBHOOK_DENY_LIST=
 WEBHOOK_ERROR_ALLOW_LIST=
@@ -138,6 +139,7 @@ run: ## Start a Gotenberg container
 	--prometheus-collect-interval=$(PROMETHEUS_COLLECT_INTERVAL) \
 	--prometheus-disable-route-logging=$(PROMETHEUS_DISABLE_ROUTE_LOGGING) \
 	--prometheus-disable-collect=$(PROMETHEUS_DISABLE_COLLECT) \
+	--webhook-enable-sync-mode="$(WEBHOOK_ENABLE_SYNC_MODE)" \
 	--webhook-allow-list="$(WEBHOOK_ALLOW_LIST)" \
 	--webhook-deny-list="$(WEBHOOK_DENY_LIST)" \
 	--webhook-error-allow-list=$(WEBHOOK_ERROR_ALLOW_LIST) \
diff --git a/pkg/modules/webhook/middleware.go b/pkg/modules/webhook/middleware.go
index 6dbef99f..f5d870d3 100644
--- a/pkg/modules/webhook/middleware.go
+++ b/pkg/modules/webhook/middleware.go
@@ -235,18 +235,7 @@ func webhookMiddleware(w *Webhook) api.Middleware {
 						}
 					}
 
-					webhookSyncHeader := c.Request().Header.Get("Gotenberg-Webhook-Sync")
-					webhookSync := false
-					if webhookSyncHeader != "" {
-						var err error
-						webhookSync, err = strconv.ParseBool(webhookSyncHeader)
-						if err != nil {
-							return fmt.Errorf("parse webhook sync header: %w", err)
-						}
-					}
-
-					if webhookSync {
-						// Synchronous mode has been requested.
+					if w.enableSyncMode {
 						err := next(c)
 						if err != nil {
 							if errors.Is(err, api.ErrNoOutputFile) {
diff --git a/pkg/modules/webhook/webhook.go b/pkg/modules/webhook/webhook.go
index 0ff6f3f7..dd660ce8 100644
--- a/pkg/modules/webhook/webhook.go
+++ b/pkg/modules/webhook/webhook.go
@@ -18,6 +18,7 @@ func init() {
 // Webhook is a module that provides a middleware for uploading output files
 // to any destinations in an asynchronous fashion.
 type Webhook struct {
+	enableSyncMode bool
 	allowList      *regexp2.Regexp
 	denyList       *regexp2.Regexp
 	errorAllowList *regexp2.Regexp
@@ -36,6 +37,7 @@ func (w *Webhook) Descriptor() gotenberg.ModuleDescriptor {
 		ID: "webhook",
 		FlagSet: func() *flag.FlagSet {
 			fs := flag.NewFlagSet("webhook", flag.ExitOnError)
+			fs.Bool("webhook-enable-sync-mode", false, "Enable synchronous mode for the webhook feature")
 			fs.String("webhook-allow-list", "", "Set the allowed URLs for the webhook feature using a regular expression")
 			fs.String("webhook-deny-list", "", "Set the denied URLs for the webhook feature using a regular expression")
 			fs.String("webhook-error-allow-list", "", "Set the allowed URLs in case of an error for the webhook feature using a regular expression")
@@ -55,6 +57,7 @@ func (w *Webhook) Descriptor() gotenberg.ModuleDescriptor {
 // Provision sets the module properties.
 func (w *Webhook) Provision(ctx *gotenberg.Context) error {
 	flags := ctx.ParsedFlags()
+	w.enableSyncMode = flags.MustBool("webhook-enable-sync-mode")
 	w.allowList = flags.MustRegexp("webhook-allow-list")
 	w.denyList = flags.MustRegexp("webhook-deny-list")
 	w.errorAllowList = flags.MustRegexp("webhook-error-allow-list")
diff --git a/test/integration/features/webhook.feature b/test/integration/features/webhook.feature
index ddd05624..fa9691c7 100644
--- a/test/integration/features/webhook.feature
+++ b/test/integration/features/webhook.feature
@@ -32,14 +32,14 @@ Feature: Webhook
     Then the webhook request header "Content-Disposition" should be "inline"
     Then there should be 1 PDF(s) in the webhook request
 
-  Scenario: Synchronous webhook processing with Gotenberg-Webhook-Sync header
-    Given I have a default Gotenberg container
+  Scenario: Synchronous
+    Given I have a Gotenberg container with the following environment variable(s):
+      | WEBHOOK_ENABLE_SYNC_MODE | true |
     Given I have a webhook server
     When I make a "POST" request to Gotenberg at the "/forms/pdfengines/flatten" endpoint with the following form data and header(s):
       | files                       | testdata/page_1.pdf                          | file   |
       | Gotenberg-Webhook-Url       | http://host.docker.internal:%d/webhook       | header |
       | Gotenberg-Webhook-Error-Url | http://host.docker.internal:%d/webhook/error | header |
-      | Gotenberg-Webhook-Sync      | true                                         | header |
     Then the response status code should be 204
     Then the webhook request header "Content-Type" should be "application/pdf"
     Then there should be 1 PDF(s) in the webhook request