diff --git a/FactorioClient.py b/FactorioClient.py
index d1b32b67..cfb59528 100644
--- a/FactorioClient.py
+++ b/FactorioClient.py
@@ -109,6 +109,12 @@ class FactorioContext(CommonContext):
             self.rcon_client.send_command(f"/ap-print [font=default-large-bold]Archipelago:[/font] "
                                           f"{text}")
 
+    def on_package(self, cmd: str, args: dict):
+        if cmd == "Connected":
+            # catch up sync anything that is already cleared.
+            for tech in args["checked_locations"]:
+                item_name = f"ap-{tech}-"
+                self.rcon_client.send_command(f'/ap-get-technology {item_name}\t-1')
 
 async def game_watcher(ctx: FactorioContext):
     bridge_logger = logging.getLogger("FactorioWatcher")
diff --git a/worlds/factorio/data/mod_template/control.lua b/worlds/factorio/data/mod_template/control.lua
index 57a9074a..80d344e0 100644
--- a/worlds/factorio/data/mod_template/control.lua
+++ b/worlds/factorio/data/mod_template/control.lua
@@ -373,7 +373,15 @@ commands.add_command("ap-get-technology", "Grant a technology, used by the Archi
     local item_name = chunks[1]
     local index = chunks[2]
     local source = chunks[3] or "Archipelago"
-    if progressive_technologies[item_name] ~= nil then
+    if index == -1 then -- for coop sync and restoring from an older savegame
+        tech = force.technologies[item_name]
+        if tech.researched ~= true then
+            game.print({"", "Received [technology=" .. tech.name .. "] as it is already checked.")
+            game.play_sound({path="utility/research_completed"})
+            tech.researched = true
+            return
+        end
+    elif progressive_technologies[item_name] ~= nil then
         if global.index_sync[index] == nil then -- not yet received prog item
             global.index_sync[index] = item_name
             local tech_stack = progressive_technologies[item_name]