diff --git a/config/mml/subscriber/udm_sub_mml_config.yaml b/config/mml/subscriber/udm_sub_mml_config.yaml
index a98bdfb2..0769e0ea 100644
--- a/config/mml/subscriber/udm_sub_mml_config.yaml
+++ b/config/mml/subscriber/udm_sub_mml_config.yaml
@@ -151,7 +151,7 @@ udm:
             comment: ""
           - name: "msisdn"
             type: "string"
-            optional: "true"
+            optional: "false"
             filter: ""
             display: "MSISDN"
             comment: ""
@@ -288,7 +288,7 @@ udm:
             comment: ""
           - name: "start_msisdn"
             type: "string"
-            optional: "true"
+            optional: "false"
             filter: ""
             display: "MSISDN"
             comment: ""