diff --git a/core/src/com/unciv/models/ruleset/Building.kt b/core/src/com/unciv/models/ruleset/Building.kt
index fd24aa0a0d..97abf29242 100644
--- a/core/src/com/unciv/models/ruleset/Building.kt
+++ b/core/src/com/unciv/models/ruleset/Building.kt
@@ -30,7 +30,7 @@ import kotlin.math.pow
 class Building : RulesetStatsObject(), INonPerpetualConstruction {
 
     override var requiredTech: String? = null
-    override var cost: Int = 0
+    override var cost: Int = -1
 
     var maintenance = 0
     private var percentStatBonus: Stats? = null