diff --git a/atst/filters.py b/atst/filters.py
index 2b54572e..011d930b 100644
--- a/atst/filters.py
+++ b/atst/filters.py
@@ -30,6 +30,8 @@ def justCents(value):
 
 
 def usPhone(number):
+    if not number:
+        return ""
     phone = re.sub(r"\D", "", number)
     return "+1 ({}) {} - {}".format(phone[0:3], phone[3:6], phone[6:])
 
diff --git a/tests/test_filters.py b/tests/test_filters.py
index 5c091faa..f35bb659 100644
--- a/tests/test_filters.py
+++ b/tests/test_filters.py
@@ -1,6 +1,6 @@
 import pytest
 
-from atst.filters import dollars, renderAuditEvent
+from atst.filters import dollars, renderAuditEvent, usPhone
 from atst.models import AuditEvent
 
 
@@ -28,3 +28,9 @@ def test_render_audit_event_with_unknown_resource_type():
     event = AuditEvent(resource_type="boat")
     result = renderAuditEvent(event)
     assert "<article" in result
+
+
+def test_usPhone():
+    assert usPhone("1234567890") == "+1 (123) 456 - 7890"
+    assert usPhone(number=None) == ""
+    assert usPhone(number="") == ""