diff --git a/plugin/src/main/java/org/elasticsearch/xpack/ml/job/messages/Messages.java b/plugin/src/main/java/org/elasticsearch/xpack/ml/job/messages/Messages.java
index f98b32198b1..19ebc3efbce 100644
--- a/plugin/src/main/java/org/elasticsearch/xpack/ml/job/messages/Messages.java
+++ b/plugin/src/main/java/org/elasticsearch/xpack/ml/job/messages/Messages.java
@@ -31,8 +31,8 @@ public final class Messages {
 
     public static final String INCONSISTENT_ID =
             "Inconsistent {0}; ''{1}'' specified in the body differs from ''{2}'' specified as a URL argument";
-    public static final String INVALID_ID =
-            "Invalid {0}; ''{1}'' must be lowercase alphanumeric, may contain hyphens or underscores, may not start with underscore";
+    public static final String INVALID_ID = "Invalid {0}; ''{1}'' can contain lowercase alphanumeric (a-z and 0-9), hyphens or " +
+            "underscores; must start and end with alphanumeric";
 
     public static final String JOB_AUDIR_DATAFEED_DATA_SEEN_AGAIN = "Datafeed has started retrieving data again";
     public static final String JOB_AUDIT_CREATED = "Job created";
diff --git a/plugin/src/test/resources/rest-api-spec/test/ml/validate.yaml b/plugin/src/test/resources/rest-api-spec/test/ml/validate.yaml
index 1e6918fdb1c..5a917c6d58c 100644
--- a/plugin/src/test/resources/rest-api-spec/test/ml/validate.yaml
+++ b/plugin/src/test/resources/rest-api-spec/test/ml/validate.yaml
@@ -59,7 +59,7 @@
 ---
 "Test job config that is invalid only because of the job ID":
   - do:
-      catch: /Invalid job_id; '_' must be lowercase alphanumeric, may contain hyphens or underscores, may not start with underscore/
+      catch: /Invalid job_id; '_' can contain lowercase alphanumeric \(a-z and 0-9\), hyphens or underscores; must start and end with alphanumeric/
       xpack.ml.validate:
         body:  >
           {