diff --git a/bazarr/CHANGELOG.md b/bazarr/CHANGELOG.md
index a245574eb..c597bb589 100644
--- a/bazarr/CHANGELOG.md
+++ b/bazarr/CHANGELOG.md
@@ -1,5 +1,8 @@
 
-## 1.5.6-3 (2026-04-20)
+## 1.5.6-4 (2026-04-22)
+- Fix Bazarr crash on startup: base_url must start with '/' for Flask blueprint registration
+
+## 1.5.6-3
 - Add Ingress support with nginx reverse proxy for sidebar integration
 - Add connection_mode option (ingress_noauth/noingress_auth/ingress_auth)
 
diff --git a/bazarr/config.yaml b/bazarr/config.yaml
index f4c57f8b3..7165cbe75 100644
--- a/bazarr/config.yaml
+++ b/bazarr/config.yaml
@@ -112,5 +112,5 @@ schema:
 slug: bazarr_nas
 udev: true
 url: https://github.com/alexbelgium/hassio-addons/tree/master/bazarr
-version: "1.5.6-3"
+version: "1.5.6-4"
 webui: "[PROTO:ssl]://[HOST]:[PORT:6767]"
diff --git a/bazarr/rootfs/etc/cont-init.d/32-nginx_ingress.sh b/bazarr/rootfs/etc/cont-init.d/32-nginx_ingress.sh
index 5bebf042b..56df012b6 100755
--- a/bazarr/rootfs/etc/cont-init.d/32-nginx_ingress.sh
+++ b/bazarr/rootfs/etc/cont-init.d/32-nginx_ingress.sh
@@ -35,16 +35,16 @@ if [ -f "$CONFIG_LOCATION" ]; then
         ingress_noauth)
             bashio::log.green "Ingress is enabled, authentication is disabled"
             bashio::log.yellow "WARNING : Make sure that the port is not exposed externally by your router to avoid a security risk !"
-            # Set base_url
-            sed -i "s/  base_url:.*/  base_url: $slug/" "$CONFIG_LOCATION"
+            # Set base_url (must start with / for Flask blueprint registration)
+            sed -i "s|  base_url:.*|  base_url: /$slug|" "$CONFIG_LOCATION"
             # Disable auth
             sed -i '/^auth:/,/^[^ ]/{ s/  type:.*/  type: null/ }' "$CONFIG_LOCATION"
             ;;
         # Ingress mode, with authentication
         ingress_auth)
             bashio::log.green "Ingress is enabled, and external authentication is enabled"
-            # Set base_url
-            sed -i "s/  base_url:.*/  base_url: $slug/" "$CONFIG_LOCATION"
+            # Set base_url (must start with / for Flask blueprint registration)
+            sed -i "s|  base_url:.*|  base_url: /$slug|" "$CONFIG_LOCATION"
             # Enable Bazarr auth when leaving ingress_noauth
             sed -i '/^auth:/,/^[^ ]/{ s/  type:.*/  type: form/ }' "$CONFIG_LOCATION"
             ;;