diff --git a/webbridge.lua b/webbridge.lua
index 7069279..50ad2ed 100644
--- a/webbridge.lua
+++ b/webbridge.lua
@@ -126,7 +126,11 @@ local function drawDashboard()
             if y >= h - 5 then break end -- Leave room for activity log
             
             local statusColor = getStatusColor(turtle)
-            local timeSince = math.floor((os.epoch("utc") - (turtle.lastSeen or 0)) / 1000)
+            local timeSince = 0
+            if turtle.lastSeen then
+                local currentTime = os.epoch("utc") or 0
+                timeSince = math.floor((currentTime - turtle.lastSeen) / 1000)
+            end
             
             monitor.setCursorPos(2, y)
             monitor.setTextColor(statusColor)