--- a/net/minecraft/world/level/chunk/ChunkGenerator.java
+++ b/net/minecraft/world/level/chunk/ChunkGenerator.java
@@ -269,7 +269,16 @@
         while (iterator.hasNext()) {
             Supplier<StructureFeature<?, ?>> supplier = (Supplier) iterator.next();
 
-            this.a((StructureFeature) supplier.get(), iregistrycustom, structuremanager, ichunkaccess, definedstructuremanager, i, biomebase);
+            // CraftBukkit start
+            StructureFeature<?, ?> structurefeature = (StructureFeature) supplier.get();
+            if (structurefeature.LIST_CODEC == StructureGenerator.STRONGHOLD) {
+                synchronized (structurefeature) {
+                    this.a((StructureFeature) supplier.get(), iregistrycustom, structuremanager, ichunkaccess, definedstructuremanager, i, biomebase);
+                }
+            } else {
+                this.a((StructureFeature) supplier.get(), iregistrycustom, structuremanager, ichunkaccess, definedstructuremanager, i, biomebase);
+            }
+            // CraftBukkit end
         }
 
     }
@@ -364,9 +373,11 @@
     }
 
     static {
-        IRegistry.a(IRegistry.CHUNK_GENERATOR, "noise", (Object) ChunkGeneratorAbstract.CODEC);
-        IRegistry.a(IRegistry.CHUNK_GENERATOR, "flat", (Object) ChunkProviderFlat.CODEC);
-        IRegistry.a(IRegistry.CHUNK_GENERATOR, "debug", (Object) ChunkProviderDebug.CODEC);
+        // CraftBukkit start - decompile errors
+        IRegistry.a(IRegistry.CHUNK_GENERATOR, "noise", ChunkGeneratorAbstract.CODEC);
+        IRegistry.a(IRegistry.CHUNK_GENERATOR, "flat", ChunkProviderFlat.CODEC);
+        IRegistry.a(IRegistry.CHUNK_GENERATOR, "debug", ChunkProviderDebug.CODEC);
+        // CraftBukkit end
         CODEC = IRegistry.CHUNK_GENERATOR.dispatchStable(ChunkGenerator::a, Function.identity());
     }
 }