diff --git a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPI.kt b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPI.kt
index db24354..bb56c3a 100644
--- a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPI.kt
+++ b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPI.kt
@@ -100,5 +100,5 @@ interface LandsAPI {
      * @param modifier A function that modifies the land's data
      * @return true if the land was modified successfully, false if the land doesn't exist
      */
-    fun modifyLand(name: String, modifier: (LandData) -> Unit): Boolean
+    fun modifyLand(name: String, modifier: (LandData) -> LandData): Boolean
 }
diff --git a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPIImpl.kt b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPIImpl.kt
index e59f795..90feda1 100644
--- a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPIImpl.kt
+++ b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/api/LandsAPIImpl.kt
@@ -49,7 +49,7 @@ class LandsAPIImpl(private val landService: LandService) : LandsAPI {
         return landService.deleteLand(land.id)
     }
     
-    override fun modifyLand(name: String, modifier: (LandData) -> Unit): Boolean {
+    override fun modifyLand(name: String, modifier: (LandData) -> LandData): Boolean {
         val land = landService.findLandsByName(name).firstOrNull() ?: return false
         return landService.modifyLand(land.id, modifier)
     }
diff --git a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/command/LandsCommand.kt b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/command/LandsCommand.kt
index 53e768b..2769b67 100644
--- a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/command/LandsCommand.kt
+++ b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/command/LandsCommand.kt
@@ -454,8 +454,9 @@ class LandsCommand(
         }
         
         service.modifyLand(land.id) { data ->
-            @Suppress("UNCHECKED_CAST")
-            action(data.parts as MutableList<Shape>)
+            val mutableParts = data.parts.toMutableList()
+            action(mutableParts)
+            data.copy(parts = mutableParts)
         }
     }
 
diff --git a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/service/LandService.kt b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/service/LandService.kt
index 31af859..63570e1 100644
--- a/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/service/LandService.kt
+++ b/lands-plugin/src/main/kotlin/net/hareworks/hcu/lands/service/LandService.kt
@@ -81,12 +81,10 @@ class LandService(private val database: Database) {
         }
     }
 
-    fun modifyLand(id: Int, modifier: (LandData) -> Unit): Boolean {
+    fun modifyLand(id: Int, modifier: (LandData) -> LandData): Boolean {
         val land = cache[id] ?: return false
-        val newParts = ArrayList(land.data.parts)
-        val newData = land.data.copy(parts = newParts)
         
-        modifier(newData)
+        val newData = modifier(land.data)
         
         transaction(database) {
             LandsTable.update({ LandsTable.id eq id }) {