diff --git a/core/src/com/unciv/ui/worldscreen/unit/UnitActions.kt b/core/src/com/unciv/ui/worldscreen/unit/UnitActions.kt
index 6d09d4a20d..af2f8264ac 100644
--- a/core/src/com/unciv/ui/worldscreen/unit/UnitActions.kt
+++ b/core/src/com/unciv/ui/worldscreen/unit/UnitActions.kt
@@ -134,6 +134,7 @@ class UnitActions {
 
         for(improvement in listOf("Fishing Boats","Oil well")) {
             if (unit.hasUnique("May create improvements on water resources") && tile.resource != null
+                    && tile.improvement==null
                     && tile.getTileResource().improvement == improvement
                     && unit.civInfo.tech.isResearched(GameBasics.TileImprovements[improvement]!!.techRequired!!)
             )