diff --git a/shiftregister/app/templatetags/shift_extras.py b/shiftregister/app/templatetags/shift_extras.py
index c6e2a42..1f34c79 100644
--- a/shiftregister/app/templatetags/shift_extras.py
+++ b/shiftregister/app/templatetags/shift_extras.py
@@ -7,6 +7,7 @@ register = template.Library()
 def duration(value):
     secs = int(value.total_seconds())
     hours = secs // (60 * 60)
-    secs = secs % (hours * 60 * 60)
+    if hours > 0:
+        secs = secs % (hours * 60 * 60)
     minutes = secs // 60
     return f"{hours}:{minutes:02d}h"