diff --git a/validator/client/src/main/java/tech/pegasys/teku/validator/client/restapi/apis/GetGraffiti.java b/validator/client/src/main/java/tech/pegasys/teku/validator/client/restapi/apis/GetGraffiti.java
index c5c2578baef..c3c962f3c14 100644
--- a/validator/client/src/main/java/tech/pegasys/teku/validator/client/restapi/apis/GetGraffiti.java
+++ b/validator/client/src/main/java/tech/pegasys/teku/validator/client/restapi/apis/GetGraffiti.java
@@ -57,6 +57,7 @@ public GetGraffiti() {
             .response(SC_OK, "Success response", RESPONSE_TYPE)
             .withAuthenticationResponses()
             .withNotFoundResponse()
+            .withNotImplementedResponse()
             .build());
   }
 
diff --git a/validator/client/src/test/resources/tech/pegasys/teku/validator/client/restapi/paths/_eth_v1_validator_{pubkey}_graffiti.json b/validator/client/src/test/resources/tech/pegasys/teku/validator/client/restapi/paths/_eth_v1_validator_{pubkey}_graffiti.json
index 9c5974f3aa6..e8216a258e8 100644
--- a/validator/client/src/test/resources/tech/pegasys/teku/validator/client/restapi/paths/_eth_v1_validator_{pubkey}_graffiti.json
+++ b/validator/client/src/test/resources/tech/pegasys/teku/validator/client/restapi/paths/_eth_v1_validator_{pubkey}_graffiti.json
@@ -58,6 +58,16 @@
           }
         }
       },
+      "501" : {
+        "description" : "Not implemented",
+        "content" : {
+          "application/json" : {
+            "schema" : {
+              "$ref" : "#/components/schemas/HttpErrorResponse"
+            }
+          }
+        }
+      },
       "400" : {
         "description" : "The request could not be processed, check the response for more information.",
         "content" : {