diff --git a/config/schema/fillpdf.schema.yml b/config/schema/fillpdf.schema.yml
index cbe58fa4595f8ccab94b9595c9f256df42da4a18..c4b27a81eb78e0e32a03e218f769010bc0b1c6a4 100644
--- a/config/schema/fillpdf.schema.yml
+++ b/config/schema/fillpdf.schema.yml
@@ -11,6 +11,9 @@ fillpdf.settings:
     remote_endpoint:
       type: string
       label: 'FillPDF Service endpoint URL without protocol'
+    fillpdf_service_api_key:
+      type: string
+      label: 'FillPDF Service API key'
     allowed_schemes:
       type: sequence
       label: 'Allowed storage schemes'