diff --git a/.mergify.yml b/.mergify.yml
deleted file mode 100644
index 849a93b..0000000
--- a/.mergify.yml
+++ /dev/null
@@ -1,10 +0,0 @@
-pull_request_rules:
-  - name: automatically merge & label scala-steward's PRs
-    conditions:
-      - author=scala-steward
-      - status-success=test
-    actions:
-      merge:
-        method: squash
-      label:
-        add: [scala-steward]
\ No newline at end of file
diff --git a/build.sbt b/build.sbt
index 95c6bd4..a3e1f78 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,5 +1,6 @@
-ThisBuild / scalaVersion := "2.12.11"
-ThisBuild / organization := "com.alejandrohdezma"
+ThisBuild / scalaVersion                  := "2.12.12"
+ThisBuild / organization                  := "com.alejandrohdezma"
+ThisBuild / pluginCrossBuild / sbtVersion := "1.2.8"
 
 addCommandAlias("ci-test", "fix --check; mdoc; scripted")
 addCommandAlias("ci-docs", "github; mdoc; headerCreateAll")
@@ -7,7 +8,7 @@ addCommandAlias("ci-publish", "github; ci-release")
 
 lazy val documentation = project
   .enablePlugins(MdocPlugin)
-  .dependsOn(allModules: _*)
+  .dependsOn(allModules)
   .settings(mdocOut := file("."))
 
 lazy val `sbt-modules` = module
diff --git a/docs/README.md b/docs/README.md
index 0787db4..424f943 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -8,7 +8,7 @@
 lazy val docs = project
 -  .settings(skip in publish := true)
 -  .dependsOn(allProjects: _*)
-+  .dependsOn(allModules: _*)
++  .dependsOn(allModules)
   .in(file("docs"))
 
 + lazy val `my-library-core` = module
@@ -67,13 +67,15 @@ Would expect the following directory structure:
 `sbt-modules` creates a special variable called `allModules` that aggregates all the modules created with `module`, so you can pass it along as a dependency to other projects in your build, like:
 
 ```sbt
-lazy val documentation = project.dependsOn(allModules: _*)
+lazy val documentation = project.dependsOn(allModules)
 
 lazy val `my-library-core` = module
 
 lazy val `my-library-plugin` = module.dependsOn(`my-library-core`)
 ```
 
+> Important ‼️ The `allModules` variable is created by listing all the directories in the `modules` directory so ensure: (1) that all your modules have a corresponding directory inside `modules` and (2) that there are no directories inside `modules` that aren't a module.
+
 ### Auto-`skip in publish`
 
 Forget about setting `skip in publish := true` again. Adding this plugin to your build will disable publishing for all the projects in the build (including the auto-generated root plugin), except for those created with `module`.
@@ -84,7 +86,7 @@ Example:
 
 ```sbt
 // Will not be published
-lazy val documentation = project.dependsOn(allmodules: _*)
+lazy val documentation = project.dependsOn(allmodules)
 
 // Will be published
 lazy val `my-library-plugin` = module.dependsOn(`my-library-core`)
diff --git a/modules/sbt-modules/src/main/scala/com/alejandrohdezma/sbt/modules/ModulesPlugin.scala b/modules/sbt-modules/src/main/scala/com/alejandrohdezma/sbt/modules/ModulesPlugin.scala
index 932987b..09cf5c6 100644
--- a/modules/sbt-modules/src/main/scala/com/alejandrohdezma/sbt/modules/ModulesPlugin.scala
+++ b/modules/sbt-modules/src/main/scala/com/alejandrohdezma/sbt/modules/ModulesPlugin.scala
@@ -16,27 +16,53 @@
 
 package com.alejandrohdezma.sbt.modules
 
-import scala.collection.mutable
 import scala.language.experimental.macros
 import scala.reflect.macros._
 
 import sbt.Keys._
 import sbt._
 
-@SuppressWarnings(Array("scalafix:Disable.scala.collection.mutable", "scalafix:DisableSyntax.implicitConversion"))
+@SuppressWarnings(
+  Array(
+    "scalafix:Disable.scala.collection.mutable",
+    "scalafix:DisableSyntax.implicitConversion",
+    "scalafix:Disable.blocking.io"
+  )
+)
 object ModulesPlugin extends AutoPlugin {
 
   override def trigger = allRequirements
 
   object autoImport {
 
-    /** List of all modules created with [[module]] */
-    val allModules: mutable.MutableList[Project] = mutable.MutableList[Project]()
+    implicit class ProjectOpsWithProjectReferenceList(private val project: Project) extends AnyVal {
+
+      /** Adds classpath dependencies on internal or external projects. */
+      def dependsOn(deps: List[ProjectReference]): Project =
+        project.dependsOn(deps: _*)
+
+      /**
+       * Adds projects to be aggregated.  When a user requests a task to run on this project from the command line,
+       * the task will also be run in aggregated projects.
+       */
+      def aggregate(refs: List[ProjectReference]): Project =
+        project.aggregate(refs: _*)
+
+    }
 
-    implicit def MutableListProject2ListClasspathDependency(
-        list: mutable.MutableList[Project]
+    /** List of all modules created with [[module]] */
+    val allModules: List[ProjectReference] =
+      Option(file("./modules"))
+        .filter(_.isDirectory())
+        .fold(List.empty[File])(_.listFiles.toList)
+        .filter(_.isDirectory())
+        .map(_.getName())
+        .map(LocalProject(_))
+
+    implicit def ListProject2ListClasspathDependency(
+        list: List[ProjectReference]
     ): List[ClasspathDep[ProjectReference]] =
-      list.map(classpathDependency(_)).toList
+      list.map(classpathDependency(_))
 
     /**
      * Creates a new Project with `modules` as base directory.
@@ -64,12 +90,7 @@ object ModulesPlugin extends AutoPlugin {
       val name = c.Expr[String](Literal(Constant(enclosingValName)))
 
       reify {
-        val project = Project(name.splice, file("modules") / name.splice)
-          .settings(skip in publish := false)
-
-        ModulesPlugin.autoImport.allModules += project
-
-        project
+        Project(name.splice, file("modules") / name.splice).settings(skip in publish := false)
       }
     }
 
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/all-modules/modules/a/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/all-modules/modules/a/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/all-modules/modules/b/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/all-modules/modules/b/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/all-modules/modules/c/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/all-modules/modules/c/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/simple/modules/a/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/simple/modules/a/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/simple/modules/b/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/simple/modules/b/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/build.sbt b/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/build.sbt
index 9401f63..f652a2e 100644
--- a/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/build.sbt
+++ b/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/build.sbt
@@ -5,8 +5,8 @@ lazy val c = project.dependsOn(allModules: _*)
 
 TaskKey[Unit]("check", "Checks c depends on a & b using `allModules`") := {
   val expected = List(
-    ClasspathDependency(LocalProject("b"), None),
-    ClasspathDependency(LocalProject("a"), None)
+    ClasspathDependency(LocalProject("a"), None),
+    ClasspathDependency(LocalProject("b"), None)
   )
 
   assert(c.dependencies == expected, s"Found: ${c.dependencies}\nExpected: $expected")
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/modules/a/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/modules/a/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/modules/b/.noop b/modules/sbt-modules/src/sbt-test/sbt-modules/skip-in-publish/modules/b/.noop
new file mode 100644
index 0000000..e69de29
diff --git a/project/build.properties b/project/build.properties
index 0837f7a..6db9842 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.3.13
+sbt.version=1.4.0