diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 03212aa94..072a7595d 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -371,13 +371,16 @@ object Defaults extends BuildCommon {
       }).value
   )
 
-  def paths = Seq(
+  // Appended to JvmPlugin.projectSettings
+  def paths: Seq[Setting[_]] = Seq(
     baseDirectory := thisProject.value.base,
     target := baseDirectory.value / "target",
     historyPath := (historyPath or target(t => Option(t / ".history"))).value,
     sourceDirectory := baseDirectory.value / "src",
     sourceManaged := crossTarget.value / "src_managed",
-    resourceManaged := crossTarget.value / "resource_managed"
+    resourceManaged := crossTarget.value / "resource_managed",
+    // Adds subproject build.sbt files to the global list of build files to monitor
+    Scope.Global / checkBuildSources / fileInputs += baseDirectory.value.toGlob / "*.sbt"
   )
 
   lazy val configPaths = sourceConfigPaths ++ resourceConfigPaths ++ outputConfigPaths
diff --git a/main/src/main/scala/sbt/internal/nio/CheckBuildSources.scala b/main/src/main/scala/sbt/internal/nio/CheckBuildSources.scala
index 54a0fe752..782975b75 100644
--- a/main/src/main/scala/sbt/internal/nio/CheckBuildSources.scala
+++ b/main/src/main/scala/sbt/internal/nio/CheckBuildSources.scala
@@ -13,7 +13,10 @@ import sbt.SlashSyntax0._
 import sbt.io.syntax._
 import sbt.nio.FileChanges
 import sbt.nio.Keys._
-import sbt.nio.file.{ Glob, RecursiveGlob }
+import sbt.nio.file.{ Glob, ** }
+import sbt.nio.file.syntax._
+
+import scala.annotation.tailrec
 
 private[sbt] object CheckBuildSources {
   private[sbt] def needReloadImpl: Def.Initialize[Task[StateTransform]] = Def.task {
@@ -60,15 +63,20 @@ private[sbt] object CheckBuildSources {
   private[sbt] def buildSourceFileInputs: Def.Initialize[Seq[Glob]] = Def.setting {
     if (onChangedBuildSource.value != IgnoreSourceChanges) {
       val baseDir = (LocalRootProject / baseDirectory).value
-      val sourceFilter = "*.{sbt,scala,java}"
       val projectDir = baseDir / "project"
-      Seq(
-        Glob(baseDir, "*.sbt"),
-        Glob(projectDir, sourceFilter),
-        // We only want to recursively look in source because otherwise we have to search
-        // the project target directories which is expensive.
-        Glob(projectDir / "src", RecursiveGlob / sourceFilter),
-      )
+      @tailrec
+      def projectGlobs(projectDir: File, globs: Seq[Glob]): Seq[Glob] = {
+        val glob = projectDir.toGlob
+        val base = Seq(
+          glob / "*.{sbt,scala,java}",
+          // We only want to recursively look in source because otherwise we have to search
+          // the project target directories which is expensive.
+          glob / "src" / ** / "*.{scala,java}"
+        )
+        val nextLevel = projectDir / "project"
+        if (nextLevel.exists) projectGlobs(nextLevel, base) else base
+      }
+      projectGlobs(projectDir, baseDir.toGlob / "*.sbt" :: Nil)
     } else Nil
   }
 }
diff --git a/sbt/src/sbt-test/nio/reload/.scalafmt.conf b/sbt/src/sbt-test/nio/reload/.scalafmt.conf
new file mode 100644
index 000000000..8a81e8505
--- /dev/null
+++ b/sbt/src/sbt-test/nio/reload/.scalafmt.conf
@@ -0,0 +1,21 @@
+version = 2.0.0
+maxColumn = 100
+project.git = true
+project.excludeFilters = [ "\\Wsbt-test\\W", "\\Winput_sources\\W", "\\Wcontraband-scala\\W" ]
+
+# http://docs.scala-lang.org/style/scaladoc.html recommends the JavaDoc style.
+# scala/scala is written that way too https://github.com/scala/scala/blob/v2.12.2/src/library/scala/Predef.scala
+docstrings = JavaDoc
+
+# This also seems more idiomatic to include whitespace in import x.{ yyy }
+spaces.inImportCurlyBraces = true
+
+# This is more idiomatic Scala.
+# http://docs.scala-lang.org/style/indentation.html#methods-with-numerous-arguments
+align.openParenCallSite = false
+align.openParenDefnSite = false
+
+# For better code clarity
+danglingParentheses = true
+
+trailingCommas = preserve
diff --git a/sbt/src/sbt-test/nio/reload/build.sbt b/sbt/src/sbt-test/nio/reload/build.sbt
index c143ba056..c5e320e75 100644
--- a/sbt/src/sbt-test/nio/reload/build.sbt
+++ b/sbt/src/sbt-test/nio/reload/build.sbt
@@ -11,3 +11,5 @@ exists := {
 }
 
 Global / onChangedBuildSource := ReloadOnSourceChanges
+
+val sub = project
diff --git a/sbt/src/sbt-test/nio/reload/changes/ScalafmtVersion.scala b/sbt/src/sbt-test/nio/reload/changes/ScalafmtVersion.scala
new file mode 100644
index 000000000..42ad05178
--- /dev/null
+++ b/sbt/src/sbt-test/nio/reload/changes/ScalafmtVersion.scala
@@ -0,0 +1,3 @@
+object ScalafmtVersion {
+  val value = "2.0.4"
+}
\ No newline at end of file
diff --git a/sbt/src/sbt-test/nio/reload/changes/broken.sbt b/sbt/src/sbt-test/nio/reload/changes/broken.sbt
index 57e15cd57..5210c3db2 100644
--- a/sbt/src/sbt-test/nio/reload/changes/broken.sbt
+++ b/sbt/src/sbt-test/nio/reload/changes/broken.sbt
@@ -8,3 +8,5 @@ exists := {
 }
 
 Global / onChangedBuildSource := ReloadOnSourceChanges
+
+val sub = project
diff --git a/sbt/src/sbt-test/nio/reload/changes/sub.sbt b/sbt/src/sbt-test/nio/reload/changes/sub.sbt
new file mode 100644
index 000000000..f0ce2b852
--- /dev/null
+++ b/sbt/src/sbt-test/nio/reload/changes/sub.sbt
@@ -0,0 +1 @@
+libraryDependencies += "org.scala-sbt" % "sbt" % "1.3.0"
\ No newline at end of file
diff --git a/sbt/src/sbt-test/nio/reload/changes/working.sbt b/sbt/src/sbt-test/nio/reload/changes/working.sbt
index c143ba056..c5e320e75 100644
--- a/sbt/src/sbt-test/nio/reload/changes/working.sbt
+++ b/sbt/src/sbt-test/nio/reload/changes/working.sbt
@@ -11,3 +11,5 @@ exists := {
 }
 
 Global / onChangedBuildSource := ReloadOnSourceChanges
+
+val sub = project
diff --git a/sbt/src/sbt-test/nio/reload/project/plugins.sbt b/sbt/src/sbt-test/nio/reload/project/plugins.sbt
new file mode 100644
index 000000000..99c853f12
--- /dev/null
+++ b/sbt/src/sbt-test/nio/reload/project/plugins.sbt
@@ -0,0 +1,8 @@
+libraryDependencies ++= {
+  if (ScalafmtVersion.value == "2.0.4") {
+    val sbtV = (sbtBinaryVersion in pluginCrossBuild).value
+    val scalaV = (scalaBinaryVersion in update).value
+    val dep = "org.scalameta" % "sbt-scalafmt" % ScalafmtVersion.value
+    sbt.Defaults.sbtPluginExtra(dep, sbtV, scalaV) :: Nil
+  } else Nil
+}
diff --git a/sbt/src/sbt-test/nio/reload/project/project/ScalafmtVersion.scala b/sbt/src/sbt-test/nio/reload/project/project/ScalafmtVersion.scala
new file mode 100644
index 000000000..d21e33494
--- /dev/null
+++ b/sbt/src/sbt-test/nio/reload/project/project/ScalafmtVersion.scala
@@ -0,0 +1,3 @@
+object ScalafmtVersion {
+  val value = "2.0.3"
+}
\ No newline at end of file
diff --git a/sbt/src/sbt-test/nio/reload/sub/build.sbt b/sbt/src/sbt-test/nio/reload/sub/build.sbt
new file mode 100644
index 000000000..e69de29bb
diff --git a/sbt/src/sbt-test/nio/reload/sub/src/main/scala/Test.scala b/sbt/src/sbt-test/nio/reload/sub/src/main/scala/Test.scala
new file mode 100644
index 000000000..405e020be
--- /dev/null
+++ b/sbt/src/sbt-test/nio/reload/sub/src/main/scala/Test.scala
@@ -0,0 +1,3 @@
+object Test {
+  val x = sbt.Keys
+}
\ No newline at end of file
diff --git a/sbt/src/sbt-test/nio/reload/test b/sbt/src/sbt-test/nio/reload/test
index abfe64f5e..26ef1a9ff 100644
--- a/sbt/src/sbt-test/nio/reload/test
+++ b/sbt/src/sbt-test/nio/reload/test
@@ -17,3 +17,15 @@ $ copy-file changes/working.sbt build.sbt
 > foo foo; reload
 
 > exists foo
+
+-> compile
+
+$ copy-file changes/sub.sbt sub/build.sbt
+
+> compile
+
+-> scalafmt
+
+$ copy-file changes/ScalafmtVersion.scala project/project/ScalafmtVersion.scala
+
+> scalafmt