diff --git a/ocflib/account/utils.py b/ocflib/account/utils.py
index ca120211..e7d8d6e8 100644
--- a/ocflib/account/utils.py
+++ b/ocflib/account/utils.py
@@ -40,7 +40,7 @@ def extract_username_from_principal(principal):
     'ckuehl'
     """
 
-    REGEX = '^([a-z]{3,16})(/[a-z]*)?@OCF\\.BERKELEY\\.EDU$'
+    REGEX = '^([a-z][a-z0-9]{2,15})(/[a-z]*)?@OCF\\.BERKELEY\\.EDU$'
     match = re.match(REGEX, principal)
 
     if not match:
diff --git a/ocflib/account/validators.py b/ocflib/account/validators.py
index 3b776c92..0e14ea20 100644
--- a/ocflib/account/validators.py
+++ b/ocflib/account/validators.py
@@ -344,8 +344,11 @@ def validate_username(username, check_exists=False):
     if not 3 <= len(username) <= 16:
         raise ValueError('Username must be between 3 and 16 characters.')
 
-    if not all(c.islower() for c in username):
-        raise ValueError('Username must be all lowercase letters.')
+    if not username[0].islower():
+        raise ValueError('Username must begin with a lowercase character')
+
+    if not all(c.islower() or c.isdigit() for c in username):
+        raise ValueError('Username must be only lowercase and numeric characters.')
 
     if check_exists and not user_exists(username):
         raise ValueError('Username does not exist.')
diff --git a/tests/account/validators_test.py b/tests/account/validators_test.py
index 216745cb..ac1a4e86 100644
--- a/tests/account/validators_test.py
+++ b/tests/account/validators_test.py
@@ -26,7 +26,6 @@ class TestValidateUsername:
         'Ckuehl',
         'ckuehl!',
         '123123',
-        'f00f00',
     ])
     def test_failure(self, username):
         with pytest.raises(ValueError):