diff --git a/src/main/java/net/minecraftforge/fml/common/registry/FMLControlledNamespacedRegistry.java b/src/main/java/net/minecraftforge/fml/common/registry/FMLControlledNamespacedRegistry.java
index 5a9e5a0bf1..5b874d2cfd 100644
--- a/src/main/java/net/minecraftforge/fml/common/registry/FMLControlledNamespacedRegistry.java
+++ b/src/main/java/net/minecraftforge/fml/common/registry/FMLControlledNamespacedRegistry.java
@@ -45,6 +45,7 @@ import net.minecraft.util.registry.RegistryNamespacedDefaultedByKey;
 import net.minecraftforge.fml.common.FMLLog;
 import net.minecraftforge.fml.common.functions.GenericIterableFactory;
 import net.minecraftforge.fml.common.registry.RegistryDelegate.Delegate;
+import net.minecraftforge.fml.relauncher.ReflectionHelper;
 
 public class FMLControlledNamespacedRegistry<I extends IForgeRegistryEntry<I>> extends RegistryNamespacedDefaultedByKey<ResourceLocation, I> implements IForgeRegistry<I>
 {
@@ -98,7 +99,7 @@ public class FMLControlledNamespacedRegistry<I extends IForgeRegistryEntry<I>> e
         this.optionalDefaultKey = defaultKey;
         this.minId = minIdValue;
         this.maxId = maxIdValue;
-        this.availabilityMap = new BitSet(maxIdValue + 1);
+        this.availabilityMap = new BitSet(Math.min(maxIdValue + 1, 0xFFFF)); //No need to pre-allocate large sets, it will resize when we need it.
         this.isDelegated = IForgeRegistryEntry.Impl.class.isAssignableFrom(type);
         this.addCallback = addCallback;
         this.clearCallback = clearCallback;
@@ -112,6 +113,15 @@ public class FMLControlledNamespacedRegistry<I extends IForgeRegistryEntry<I>> e
 
     void validateContent(ResourceLocation registryName)
     {
+        try
+        {
+            ReflectionHelper.findMethod(BitSet.class, this.availabilityMap, new String[]{"trimToSize"}).invoke(this.availabilityMap);
+        }
+        catch (Exception e)
+        {
+            //We don't care... Just a micro-optimization
+        }
+
         for (I obj : typeSafeIterable())
         {
             int id = getId(obj);