diff --git a/lib/awful/tag.lua.in b/lib/awful/tag.lua.in
index e3399e5..3aa4eee 100644
--- a/lib/awful/tag.lua.in
+++ b/lib/awful/tag.lua.in
@@ -270,22 +270,26 @@ end
 -- @param t tag object
 -- @param s Screen number
 function tag.setscreen(t, s)
-    local s = s or capi.mouse.screen
+    if t then
+        local s = s or capi.mouse.screen
+        local old_screen = tag.getproperty(t, "screen")
 
-    -- Keeping the old index make very little sense when changing screen
-    tag.setproperty(t, "index", nil)
+        if old_screen and old_screen ~= s then
+            -- Keeping the old index make very little sense when changing screen
+            tag.setproperty(t, "index", nil)
 
-    local old_screen = tag.getproperty(t,"screen")
+            -- Change the screen
+            tag.setproperty(t, "screen", s)
 
-    -- Change the screen
-    tag.setproperty(t, "screen", s)
+            -- Make sure the client's screen matches its tags
+            for _, c in ipairs(t:clients()) do
+                c.screen = s --Move all clients
+                c:tags({t})
+            end
 
-    -- Make sure the client's screen matches its tags
-    for k,c in ipairs(t:clients()) do
-        c.screen = s --Move all clients
-        c:tags({t})
+            tag.history.restore(old_screen, 1)
+        end
     end
-    tag.history.restore(old_screen,1)
 end
 
 --- Get a tag's screen