diff --git a/Handler/CreateChallenge.hs b/Handler/CreateChallenge.hs
index bc5c2ce..1b57f12 100644
--- a/Handler/CreateChallenge.hs
+++ b/Handler/CreateChallenge.hs
@@ -73,7 +73,7 @@ postCreateChallengeR = do
           then
             runViewProgress $ doCreateChallenge challengeData
           else
-            runViewProgress $ (flip err) "unexpected challenge ID (use only lower-case letters, digits and hyphens, start with a letter)"
+            runViewProgress $ (flip err) "unexpected challenge ID (use only lower-case letters, digits and hyphens, start with a letter or a digit)"
       else
         runViewProgress $ (flip err) "MUST BE AN ADMIN TO CREATE A CHALLENGE"
 
diff --git a/Handler/Shared.hs b/Handler/Shared.hs
index 8a4b773..6ffd64d 100644
--- a/Handler/Shared.hs
+++ b/Handler/Shared.hs
@@ -642,7 +642,7 @@ findFilePossiblyCompressed baseFilePath = do
     (h:_) -> Just h
 
 localIdRegexp :: Regex
-localIdRegexp = makeRegexOpts defaultCompOpt{newSyntax=True} defaultExecOpt ("\\`[a-z][-a-z0-9]{0,63}\\'" ::String)
+localIdRegexp = makeRegexOpts defaultCompOpt{newSyntax=True} defaultExecOpt ("\\`[a-z0-9][-a-z0-9]{0,63}\\'" ::String)
 
 unwantedLocalIds :: [Text]
 unwantedLocalIds = ["git",
diff --git a/messages/en.msg b/messages/en.msg
index 247d793..cf8f05d 100644
--- a/messages/en.msg
+++ b/messages/en.msg
@@ -19,7 +19,7 @@ AboutMe: about me
 AccountName: name
 AccountNameTooltip: your human-readable name (to be shown on the leaderboard)
 Id: ID
-IdTooltip: to be used in the URLs for your repos (only lower-case letters, digits or hyphens, must start with a lower-case letter), once set cannot be changed!
+IdTooltip: to be used in the URLs for your repos (only lower-case letters, digits or hyphens, must start with a lower-case letter or a digit), once set cannot be changed!
 SshPubKey: your SSH public key
 SshPubKeyTooltip: needed if you want to access repos hosted on Gonito.net (usually ".ssh/id_rsa.pub" in your home directory after you generated private/public key pair)
 Home: home
@@ -65,7 +65,7 @@ RestoreSubmission: restore submission
 ParameterName: parameter name
 ParameterValue: parameter value
 ChallengeName: computer-friendly name ("slug")
-ChallengeNameTooltip: to be used in the URLs (only lower-case letters, digits or hyphens, must start with a lower-case letter), once set cannot be changed!
+ChallengeNameTooltip: to be used in the URLs (only lower-case letters, digits or hyphens, must start with a lower-case letter or a digit), once set cannot be changed!
 FilterCondition: filter condition
 FilterConditionTooltip: the condition used to pre-select all submission — an extra graph will be drawed for all submissions matching this condition (not necessarily the target condition)
 TargetCondition: target condition