diff --git a/utils/warden/src/main/java/org/onlab/warden/Warden.java b/utils/warden/src/main/java/org/onlab/warden/Warden.java
index 8ce6037..61091b6 100644
--- a/utils/warden/src/main/java/org/onlab/warden/Warden.java
+++ b/utils/warden/src/main/java/org/onlab/warden/Warden.java
@@ -169,7 +169,7 @@
     synchronized String borrowCell(String userName, String sshKey, int minutes,
                                    String cellSpec) {
         checkNotNull(userName, USER_NOT_NULL);
-        checkArgument(userName.matches("[\\w]+"), "Invalid user name %s", userName);
+        checkArgument(userName.matches("[\\w.-]+"), "Invalid user name %s", userName);
         checkNotNull(sshKey, KEY_NOT_NULL);
         checkArgument(minutes < MAX_MINUTES, "Number of minutes must be less than %d", MAX_MINUTES);
         checkArgument(minutes >= 0, "Number of minutes must be non-negative");