diff --git a/core/src/com/unciv/logic/GameInfo.kt b/core/src/com/unciv/logic/GameInfo.kt
index f41c26c7a5..4757864d5e 100644
--- a/core/src/com/unciv/logic/GameInfo.kt
+++ b/core/src/com/unciv/logic/GameInfo.kt
@@ -3,6 +3,7 @@ package com.unciv.logic
 import com.unciv.Constants
 import com.unciv.UncivGame
 import com.unciv.UncivGame.Version
+import com.unciv.json.json
 import com.unciv.logic.BackwardCompatibility.convertEncampmentData
 import com.unciv.logic.BackwardCompatibility.convertFortify
 import com.unciv.logic.BackwardCompatibility.guaranteeUnitPromotions
@@ -35,9 +36,11 @@ import com.unciv.models.ruleset.nation.Difficulty
 import com.unciv.models.ruleset.unique.UniqueType
 import com.unciv.ui.audio.MusicMood
 import com.unciv.ui.audio.MusicTrackChooserFlags
+import com.unciv.ui.screens.savescreens.Gzip
 import com.unciv.ui.screens.worldscreen.status.NextTurnProgress
 import com.unciv.utils.DebugUtils
 import com.unciv.utils.debug
+import java.security.MessageDigest
 import java.util.UUID
 
 
@@ -100,6 +103,7 @@ class GameInfo : IsPartOfGameInfoSerialization, HasGameInfoSerializationVersion
     var currentPlayer = ""
     var currentTurnStartTime = 0L
     var gameId = UUID.randomUUID().toString() // random string
+    var checksum = ""
 
     var victoryData:VictoryData? = null
 
@@ -272,6 +276,16 @@ class GameInfo : IsPartOfGameInfoSerialization, HasGameInfoSerializationVersion
         return year.toInt()
     }
 
+    fun calculateChecksum():String {
+        val oldChecksum = checksum
+        checksum = "" // Checksum calculation cannot include old checksum, obvs
+        val bytes = MessageDigest
+            .getInstance("SHA-1")
+            .digest(json().toJson(this).toByteArray())
+        checksum = oldChecksum
+        return Gzip.encode(bytes)
+    }
+
     //endregion
     //region State changing functions
 
diff --git a/core/src/com/unciv/logic/civilization/managers/PolicyManager.kt b/core/src/com/unciv/logic/civilization/managers/PolicyManager.kt
index c297ad7ff7..d3921672c8 100644
--- a/core/src/com/unciv/logic/civilization/managers/PolicyManager.kt
+++ b/core/src/com/unciv/logic/civilization/managers/PolicyManager.kt
@@ -211,6 +211,8 @@ class PolicyManager : IsPartOfGameInfoSerialization {
             if (unique.conditionals.any {it.type == UniqueType.TriggerUponAdoptingPolicyOrBelief && it.params[0] == policy.name})
                 UniqueTriggerActivation.triggerCivwideUnique(unique, civInfo, triggerNotificationText = triggerNotificationText)
 
+        civInfo.cache.updateCivResources()
+
         // This ALSO has the side-effect of updating the CivInfo statForNextTurn so we don't need to call it explicitly
         for (cityInfo in civInfo.cities) cityInfo.cityStats.update()
 
diff --git a/core/src/com/unciv/logic/files/UncivFiles.kt b/core/src/com/unciv/logic/files/UncivFiles.kt
index 7e9e95fefa..db20695e9f 100644
--- a/core/src/com/unciv/logic/files/UncivFiles.kt
+++ b/core/src/com/unciv/logic/files/UncivFiles.kt
@@ -18,8 +18,8 @@ import com.unciv.models.metadata.GameSettings
 import com.unciv.models.metadata.doMigrations
 import com.unciv.models.metadata.isMigrationNecessary
 import com.unciv.ui.screens.savescreens.Gzip
-import com.unciv.utils.Log
 import com.unciv.utils.Concurrency
+import com.unciv.utils.Log
 import com.unciv.utils.debug
 import kotlinx.coroutines.Job
 import java.io.File
@@ -371,8 +371,10 @@ class UncivFiles(
         }
 
         /** Returns gzipped serialization of [game], optionally gzipped ([forceZip] overrides [saveZipped]) */
-        fun gameInfoToString(game: GameInfo, forceZip: Boolean? = null): String {
+        fun gameInfoToString(game: GameInfo, forceZip: Boolean? = null, updateChecksum:Boolean=true): String {
             game.version = GameInfo.CURRENT_COMPATIBILITY_VERSION
+
+            if (updateChecksum) game.checksum = game.calculateChecksum()
             val plainJson = json().toJson(game)
             return if (forceZip ?: saveZipped) Gzip.zip(plainJson) else plainJson
         }
diff --git a/core/src/com/unciv/logic/multiplayer/storage/OnlineMultiplayerServer.kt b/core/src/com/unciv/logic/multiplayer/storage/OnlineMultiplayerServer.kt
index 05d38938b5..d5f3925e01 100644
--- a/core/src/com/unciv/logic/multiplayer/storage/OnlineMultiplayerServer.kt
+++ b/core/src/com/unciv/logic/multiplayer/storage/OnlineMultiplayerServer.kt
@@ -102,7 +102,7 @@ class OnlineMultiplayerServer(
      * @throws MultiplayerAuthException if the authentication failed
      */
     suspend fun tryUploadGame(gameInfo: GameInfo, withPreview: Boolean) {
-        val zippedGameInfo = UncivFiles.gameInfoToString(gameInfo, forceZip = true)
+        val zippedGameInfo = UncivFiles.gameInfoToString(gameInfo, forceZip = true, updateChecksum = true)
         fileStorage().saveFileData(gameInfo.gameId, zippedGameInfo)
 
         // We upload the preview after the game because otherwise the following race condition will happen:
diff --git a/core/src/com/unciv/ui/screens/savescreens/Gzip.kt b/core/src/com/unciv/ui/screens/savescreens/Gzip.kt
index 42bc79be7c..22cfeb0d0c 100644
--- a/core/src/com/unciv/ui/screens/savescreens/Gzip.kt
+++ b/core/src/com/unciv/ui/screens/savescreens/Gzip.kt
@@ -10,8 +10,8 @@ import java.util.zip.GZIPOutputStream
 
 object Gzip {
 
-    fun zip(data:String):String = encoder(compress(data))
-    fun unzip(data:String):String  = decompress(decoder(data))
+    fun zip(data:String):String = encode(compress(data))
+    fun unzip(data:String):String  = decompress(decode(data))
 
     private fun compress(data: String): ByteArray {
         val bos = ByteArrayOutputStream(data.length)
@@ -40,11 +40,11 @@ object Gzip {
     }
 
 
-    private fun encoder(bytes:ByteArray): String{
+    fun encode(bytes:ByteArray): String{
         return String(Base64Coder.encode(bytes))
     }
 
-    private fun decoder(base64Str: String): ByteArray{
+    private fun decode(base64Str: String): ByteArray{
         return Base64Coder.decode(base64Str)
     }
 }