diff --git a/src/main/kotlin/com/replaymod/gradle/preprocess/PreprocessPlugin.kt b/src/main/kotlin/com/replaymod/gradle/preprocess/PreprocessPlugin.kt
index c3d0185..a67a422 100644
--- a/src/main/kotlin/com/replaymod/gradle/preprocess/PreprocessPlugin.kt
+++ b/src/main/kotlin/com/replaymod/gradle/preprocess/PreprocessPlugin.kt
@@ -37,7 +37,7 @@ class PreprocessPlugin : Plugin<Project> {
         val graph = rootExtension.rootNode ?: throw IllegalStateException("Preprocess graph was not configured.")
         val projectNode = graph.findNode(project.name) ?: throw IllegalStateException("Prepocess graph does not contain ${project.name}.")
 
-        val coreProjectFile = project.file("../mainProject")
+        val coreProjectFile = rootExtension.mainProjectFile.asFile.get()
         val coreProject = coreProjectFile.readText().trim()
         val mcVersion = projectNode.mcVersion
         project.extra["mcVersion"] = mcVersion
diff --git a/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessExtension.kt b/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessExtension.kt
index f3ede34..32251f8 100644
--- a/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessExtension.kt
+++ b/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessExtension.kt
@@ -1,13 +1,21 @@
 package com.replaymod.gradle.preprocess
 
+import org.gradle.api.Project
+import org.gradle.api.file.RegularFileProperty
 import java.io.File
 
-open class RootPreprocessExtension : ProjectGraphNodeDSL {
+open class RootPreprocessExtension(project: Project) : ProjectGraphNodeDSL {
+    val mainProjectFile: RegularFileProperty = project.objects.fileProperty()
+
     var rootNode: ProjectGraphNode? = null
         get() = field ?: linkNodes()?.also { field = it }
 
     private val nodes = mutableSetOf<Node>()
 
+    init {
+        mainProjectFile.convention(project.layout.projectDirectory.file("versions/mainProject"))
+    }
+
     fun createNode(project: String, mcVersion: Int, mappings: String): Node {
         return Node(project, mcVersion, mappings).also { nodes.add(it) }
     }
diff --git a/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessPlugin.kt b/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessPlugin.kt
index 2fbb216..4656524 100644
--- a/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessPlugin.kt
+++ b/src/main/kotlin/com/replaymod/gradle/preprocess/RootPreprocessPlugin.kt
@@ -12,6 +12,6 @@ class RootPreprocessPlugin : Plugin<Project> {
 
     override fun apply(project: Project) {
         project.logger.lifecycle("Preprocessor $version")
-        project.extensions.create("preprocess", RootPreprocessExtension::class)
+        project.extensions.create("preprocess", RootPreprocessExtension::class, project)
     }
 }