diff --git a/build.gradle b/build.gradle
index dc4d5d6..ce57008 100644
--- a/build.gradle
+++ b/build.gradle
@@ -64,6 +64,7 @@ jar {
             exclude 'META-INF', 'META-INF/**'
         }
     }
+    exclude "optifine"
 }
 
 reobf {
diff --git a/src/main/kotlin/optifine/OptifineTweakerDevWrapper.kt b/src/main/kotlin/optifine/OptifineTweakerDevWrapper.kt
new file mode 100644
index 0000000..897f6a9
--- /dev/null
+++ b/src/main/kotlin/optifine/OptifineTweakerDevWrapper.kt
@@ -0,0 +1,38 @@
+package optifine
+
+import mods.octarinecore.tryDefault
+import net.minecraft.launchwrapper.IClassTransformer
+import net.minecraft.launchwrapper.ITweaker
+import net.minecraft.launchwrapper.LaunchClassLoader
+import java.io.File
+import java.net.URLClassLoader
+import java.util.zip.ZipFile
+
+class OptifineTweakerDevWrapper : ITweaker {
+    override fun acceptOptions(p0: MutableList<String>?, p1: File?, p2: File?, p3: String?) { }
+    override fun getLaunchArguments(): Array<out String>? = Array<String>(0) {""}
+    override fun getLaunchTarget() = "net.minecraft.client.main.Main"
+    override fun injectIntoClassLoader(classLoader: LaunchClassLoader) {
+        classLoader.registerTransformer("optifine.OptifineTransformerDevWrapper")
+    }
+}
+
+/**
+ * Replacement for OptiFine's class transformer. Implements the pre-1.8.x-H5 way of operation.
+ *
+ * This class is only used in development to debug cross-mod issues with Optifine, and
+ * is not part of the release!
+ */
+class OptifineTransformerDevWrapper : IClassTransformer {
+
+    val ofZip = (this.javaClass.classLoader as? URLClassLoader)?.urLs?.find {
+        val zipFile = tryDefault(null) { ZipFile(File(it.toURI())) }
+        zipFile?.getEntry("optifine/OptiFineClassTransformer.class") != null
+    }?.let { ZipFile(File(it.toURI())) }
+
+    /**
+     * Load replacement classes from the OptiFine Jar.
+     */
+    override fun transform(name: String?, transformedName: String?, classData: ByteArray?) =
+        ofZip?.getEntry(name?.replace(".", "/") + ".class")?.let { ofZip.getInputStream(it).readBytes() } ?: classData
+}