diff --git a/patches/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java.patch b/patches/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java.patch
new file mode 100644
index 0000000000..5799fbdaac
--- /dev/null
+++ b/patches/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java.patch
@@ -0,0 +1,12 @@
+--- ../src-base/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java
++++ ../src-work/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java
+@@ -12,7 +12,8 @@
+ 
+ public class ClassInheritanceMultiMap<T> extends AbstractSet<T>
+ {
+-    private static final Set < Class<? >> field_181158_a = Sets. < Class<? >> newHashSet();
++    // Forge: Use concurrent collection to allow creating chunks from multiple threads safely
++    private static final Set < Class<? >> field_181158_a = java.util.Collections.newSetFromMap(new java.util.concurrent.ConcurrentHashMap<Class<?>, Boolean>());
+     private final Map < Class<?>, List<T >> field_180218_a = Maps. < Class<?>, List<T >> newHashMap();
+     private final Set < Class<? >> field_180216_b = Sets. < Class<? >> newIdentityHashSet();
+     private final Class<T> field_180217_c;