diff --git a/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java b/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java
index f9df7610..df2538ac 100644
--- a/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java
+++ b/src/main/java/org/embeddedt/modernfix/core/ModernFixMixinPlugin.java
@@ -41,6 +41,9 @@ public class ModernFixMixinPlugin implements IMixinConfigPlugin {
         this.logger.info("Loaded configuration file for ModernFix: {} options available, {} override(s) found",
                 config.getOptionCount(), config.getOptionOverrideCount());
 
+        if(ModernFixEarlyConfig.OPTIFINE_PRESENT)
+            this.logger.fatal("OptiFine detected. Use of ModernFix with OptiFine is not supported due to its impact on launch time and breakage of Forge features.");
+
         FastAccessTransformerList.attemptReplace();
         DFUBlaster.blastMaps();
 
diff --git a/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java b/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
index 936ba8c7..d0a50ce1 100644
--- a/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
+++ b/src/main/java/org/embeddedt/modernfix/core/config/ModernFixEarlyConfig.java
@@ -15,8 +15,23 @@ public class ModernFixEarlyConfig {
 
     private final Map<String, Option> options = new HashMap<>();
 
+    public static final boolean OPTIFINE_PRESENT;
+
+    static {
+        boolean hasOfClass = false;
+        try {
+            Class.forName("optifine.OptiFineTransformationService");
+            hasOfClass = true;
+        } catch(Throwable e) {
+        }
+        OPTIFINE_PRESENT = hasOfClass;
+    }
+
     private static boolean modPresent(String modId) {
-        return FMLLoader.getLoadingModList().getModFileById(modId) != null;
+        if(modId.equals("optifine"))
+            return OPTIFINE_PRESENT;
+        else
+            return FMLLoader.getLoadingModList().getModFileById(modId) != null;
     }
 
     private ModernFixEarlyConfig() {
@@ -71,11 +86,12 @@ public class ModernFixEarlyConfig {
         disableIfModPresent("mixin.perf.compress_biome_container", "chocolate", "betterendforge");
         disableIfModPresent("mixin.bugfix.mc218112", "performant");
         disableIfModPresent("mixin.perf.reuse_datapacks", "tac");
+        disableIfModPresent("mixin.launch.class_search_cache", "optifine");
     }
 
     private void disableIfModPresent(String configName, String... ids) {
         for(String id : ids) {
-            if(FMLLoader.getLoadingModList().getModFileById(id) != null) {
+            if(modPresent(id)) {
                 Option option = this.options.get(configName);
                 if(option != null)
                     option.addModOverride(false, id);