diff --git a/src/main/java/org/embeddedt/modernfix/classloading/FastAccessTransformerList.java b/src/main/java/org/embeddedt/modernfix/classloading/FastAccessTransformerList.java
new file mode 100644
index 00000000..21717f24
--- /dev/null
+++ b/src/main/java/org/embeddedt/modernfix/classloading/FastAccessTransformerList.java
@@ -0,0 +1,132 @@
+package org.embeddedt.modernfix.classloading;
+
+import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
+import net.minecraftforge.accesstransformer.AccessTransformer;
+import net.minecraftforge.accesstransformer.AccessTransformerEngine;
+import net.minecraftforge.accesstransformer.INameHandler;
+import net.minecraftforge.accesstransformer.Target;
+import net.minecraftforge.accesstransformer.parser.AccessTransformerList;
+import net.minecraftforge.fml.common.ObfuscationReflectionHelper;
+import org.objectweb.asm.Type;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.lang.reflect.Field;
+import java.util.Collection;
+import java.util.Map;
+import java.util.Set;
+
+public class FastAccessTransformerList extends AccessTransformerList {
+    private FastATMap accessTransformerMap;
+
+    public static void attemptReplace() {
+        AccessTransformerList masterList;
+        FastAccessTransformerList myList = new FastAccessTransformerList();
+        try {
+            Field master = AccessTransformerEngine.class.getDeclaredField("masterList");
+            master.setAccessible(true);
+            masterList = (AccessTransformerList)master.get(AccessTransformerEngine.INSTANCE);
+            Field transfomersMap = AccessTransformerList.class.getDeclaredField("accessTransformers");
+            transfomersMap.setAccessible(true);
+            Map<Target<?>, AccessTransformer> map = (Map<Target<?>, AccessTransformer>)transfomersMap.get(masterList);
+            INameHandler nameHandler = ObfuscationReflectionHelper.getPrivateValue(AccessTransformerList.class, masterList, "nameHandler");
+            myList.setNameHandler(nameHandler);
+            myList.accessTransformerMap = new FastATMap(map);
+            ObfuscationReflectionHelper.setPrivateValue(AccessTransformerList.class, myList, myList.accessTransformerMap, "accessTransformers");
+            master.set(AccessTransformerEngine.INSTANCE, myList);
+        } catch(ReflectiveOperationException e) {
+            e.printStackTrace();
+        }
+    }
+
+    @Override
+    public boolean containsClassTarget(Type type) {
+        return this.accessTransformerMap.containsType(type);
+    }
+
+    private static class FastATMap implements Map<Target<?>, AccessTransformer> {
+        private final Map<Target<?>, AccessTransformer> delegate;
+        private final Set<Type> allContainedTypes;
+
+        public FastATMap(Map<Target<?>, AccessTransformer> delegate) {
+            this.delegate = delegate;
+            this.allContainedTypes = new ObjectOpenHashSet<>();
+        }
+
+        @Override
+        public int size() {
+            return this.delegate.size();
+        }
+
+        @Override
+        public boolean isEmpty() {
+            return this.delegate.isEmpty();
+        }
+
+        @Override
+        public boolean containsKey(Object o) {
+            return this.delegate.containsKey(o);
+        }
+
+        @Override
+        public boolean containsValue(Object o) {
+            return this.delegate.containsValue(o);
+        }
+
+        @Override
+        public AccessTransformer get(Object o) {
+            return this.delegate.get(o);
+        }
+
+        @Nullable
+        @Override
+        public AccessTransformer put(Target<?> target, AccessTransformer accessTransformer) {
+            this.allContainedTypes.add(target.getASMType());
+            return this.delegate.put(target, accessTransformer);
+        }
+
+        @Override
+        public AccessTransformer remove(Object o) {
+            if(o instanceof Target) {
+                this.allContainedTypes.remove(((Target<?>)o).getASMType());
+            }
+            return this.delegate.remove(o);
+        }
+
+        @Override
+        public void putAll(@NotNull Map<? extends Target<?>, ? extends AccessTransformer> map) {
+            for(Target<?> key : map.keySet()) {
+                this.allContainedTypes.add(key.getASMType());
+            }
+            this.delegate.putAll(map);
+        }
+
+        @Override
+        public void clear() {
+            this.allContainedTypes.clear();
+            this.delegate.clear();
+        }
+
+        @NotNull
+        @Override
+        public Set<Target<?>> keySet() {
+            return this.delegate.keySet();
+        }
+
+        @NotNull
+        @Override
+        public Collection<AccessTransformer> values() {
+            return this.delegate.values();
+        }
+
+        @NotNull
+        @Override
+        public Set<Entry<Target<?>, AccessTransformer>> entrySet() {
+            return this.delegate.entrySet();
+        }
+
+        public boolean containsType(Type type) {
+            return this.allContainedTypes.contains(type);
+        }
+    }
+}
diff --git a/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java b/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java
index 3ce635a5..c6d2a883 100644
--- a/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java
+++ b/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java
@@ -9,6 +9,7 @@ import net.minecraftforge.fml.common.ObfuscationReflectionHelper;
 import net.minecraftforge.fml.loading.LoadingModList;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.embeddedt.modernfix.classloading.FastAccessTransformerList;
 import org.embeddedt.modernfix.classloading.ModernFixResourceFinder;
 import org.embeddedt.modernfix.core.config.ModernFixEarlyConfig;
 import org.embeddedt.modernfix.core.config.Option;
@@ -81,6 +82,8 @@ public class ModernFixMixinPlugin implements IMixinConfigPlugin {
             logger.error("Failed to make classloading changes", e);
         }
 
+        FastAccessTransformerList.attemptReplace();
+
         /* https://github.com/FabricMC/Mixin/pull/99 */
         try {
             Field groupMembersField = InjectorGroupInfo.class.getDeclaredField("members");