diff --git a/Core.lua b/Core.lua
index 499399c..ea0794f 100644
--- a/Core.lua
+++ b/Core.lua
@@ -616,6 +616,20 @@ function RA:AutoScan()
 end
 
 function RA:_OnUpdate(elapsed)
+    -- Elapsed can arrive as a function argument, as the global arg1, or
+    -- (on some 1.12 builds) not at all. Fall back to GetTime() deltas so
+    -- the periodic auto-scan always advances.
+    if type(elapsed) ~= "number" then elapsed = nil end
+    if not elapsed and type(arg1) == "number" then elapsed = arg1 end
+    if not elapsed and GetTime then
+        local now = GetTime()
+        if RA._lastUpdate then
+            elapsed = now - RA._lastUpdate
+        else
+            elapsed = 0
+        end
+        RA._lastUpdate = now
+    end
     elapsed = elapsed or 0
     RA._throttle = RA._throttle + elapsed
     RA._periodic = RA._periodic + elapsed
@@ -856,7 +870,12 @@ ef:SetScript("OnEvent", function()
     end
 end)
 
-ef:SetScript("OnUpdate", function()
+ef:SetScript("OnUpdate", function(_self, _elapsed)
     if not RA.initialized then return end
-    RA:_OnUpdate(arg1)
+    -- Vanilla 1.12 delivers elapsed via the global arg1; some private-server
+    -- builds pass it as a positional parameter instead. Try both.
+    local e = arg1
+    if type(e) ~= "number" then e = _elapsed end
+    if type(e) ~= "number" then e = _self end
+    RA:_OnUpdate(e)
 end)