diff --git a/core/src/com/unciv/models/ruleset/Building.kt b/core/src/com/unciv/models/ruleset/Building.kt
index cd8c4e536b..4853c33c44 100644
--- a/core/src/com/unciv/models/ruleset/Building.kt
+++ b/core/src/com/unciv/models/ruleset/Building.kt
@@ -58,7 +58,7 @@ class Building : NamedStats(), IConstruction {
     var replaces: String? = null
     var uniqueTo: String? = null
     var quote: String = ""
-    private var providesFreeBuilding: String? = null
+    var providesFreeBuilding: String? = null
     var uniques = ArrayList<String>()
     var replacementTextForUniques = ""
     val uniqueObjects: List<Unique> by lazy { uniques.map { Unique(it) } }
diff --git a/core/src/com/unciv/models/ruleset/Ruleset.kt b/core/src/com/unciv/models/ruleset/Ruleset.kt
index e3a133d424..1870f3c9a3 100644
--- a/core/src/com/unciv/models/ruleset/Ruleset.kt
+++ b/core/src/com/unciv/models/ruleset/Ruleset.kt
@@ -277,6 +277,8 @@ class Ruleset {
                 lines += "${building.name} requires ${building.requiredBuilding} which does not exist!"
             if (building.requiredBuildingInAllCities != null && !buildings.containsKey(building.requiredBuildingInAllCities!!))
                 lines += "${building.name} requires ${building.requiredBuildingInAllCities} in all cities which does not exist!"
+            if (building.providesFreeBuilding != null && !buildings.containsKey(building.providesFreeBuilding!!))
+                lines += "${building.name} provides a free ${building.providesFreeBuilding} which does not exist!"
         }
 
         for (resource in tileResources.values) {