diff --git a/ClassicalSharp/Generator/NotchyGenerator.cs b/ClassicalSharp/Generator/NotchyGenerator.cs
index 92972dbed..1f59685f9 100644
--- a/ClassicalSharp/Generator/NotchyGenerator.cs
+++ b/ClassicalSharp/Generator/NotchyGenerator.cs
@@ -347,6 +347,7 @@ namespace ClassicalSharp.Generator {
 							continue;
 						
 						int treeY = heightmap[treeZ * Width + treeX] + 1;
+						if (treeY >= Height) continue;
 						int treeHeight = 5 + rnd.Next(3);
 						
 						int index = (treeY * Length + treeZ) * Width + treeX;
diff --git a/src/Client/NotchyGenerator.c b/src/Client/NotchyGenerator.c
index d6dea53a2..47c37f054 100644
--- a/src/Client/NotchyGenerator.c
+++ b/src/Client/NotchyGenerator.c
@@ -218,6 +218,7 @@ void NotchyGen_PlantTrees() {
 					continue;
 
 				Int32 treeY = Heightmap[treeZ * Width + treeX] + 1;
+				if (treeY >= Height) continue;
 				Int32 treeHeight = 5 + Random_Next(&rnd, 3);
 
 				Int32 index = (treeY * Length + treeZ) * Width + treeX;