diff --git a/core/src/com/unciv/logic/civilization/managers/TechManager.kt b/core/src/com/unciv/logic/civilization/managers/TechManager.kt
index b6bcef9b04..cca3e2f19e 100644
--- a/core/src/com/unciv/logic/civilization/managers/TechManager.kt
+++ b/core/src/com/unciv/logic/civilization/managers/TechManager.kt
@@ -312,11 +312,22 @@ class TechManager : IsPartOfGameInfoSerialization {
         if (isNewTech)
             civInfo.popupAlerts.add(PopupAlert(AlertType.TechResearched, techName))
 
+        val revealedResources = getRuleset().tileResources.values.filter { techName == it.revealedBy }
+        var mayNeedUpdateResources = revealedResources.isNotEmpty()  // default for AI
         if (civInfo.playerType == PlayerType.Human) {
-            for (revealedResource in getRuleset().tileResources.values.filter { techName == it.revealedBy }) {
-                civInfo.gameInfo.notifyExploredResources(civInfo, revealedResource.name, 5, false)
+            mayNeedUpdateResources = false
+            for (revealedResource in revealedResources) {
+                // notifyExploredResources scans the player's owned tiles and returns false if none
+                // found with a revealed resource - keep this knowledge to avoid the update call.
+                mayNeedUpdateResources = mayNeedUpdateResources ||
+                    civInfo.gameInfo.notifyExploredResources(civInfo, revealedResource.name, 5, false)
             }
         }
+        // At least in the case of a human player hurrying research, this civ's resource availability
+        // may now be out of date - e.g. when an owned tile by luck already has an appropriate improvement.
+        // That can be seen on WorldScreenTopBar, so better update unless we know there's no resource change.
+        if (mayNeedUpdateResources)
+            civInfo.cache.updateCivResources()
 
         obsoleteOldUnits(techName)