diff --git a/.travis.yml b/.travis.yml
index f81880fd4..c7c8c5bac 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -18,6 +18,7 @@ matrix:
 
 env:
   matrix:
+    - SBT_CMD=";test:compile;scalariformCheck"
     - SBT_CMD="mimaReportBinaryIssues"
     - SBT_CMD="safeUnitTests"
     - SBT_CMD="otherUnitTests"
@@ -47,6 +48,6 @@ notifications:
 script:
   - sbt -J-XX:ReservedCodeCacheSize=128m "$SBT_CMD"
 
-  # Tricks to avoid unnecessary cache updates
-  - find $HOME/.sbt -name "*.lock" | xargs rm
-  - find $HOME/.ivy2 -name "ivydata-*.properties" | xargs rm
+before_cache:
+  - find $HOME/.ivy2 -name "ivydata-*.properties" -print -delete
+  - find $HOME/.sbt  -name "*.lock"               -print -delete
diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index e7e382783..0602cd778 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -49,11 +49,36 @@ import Keys._
 
 // incremental compiler
 import xsbt.api.Discovery
-import xsbti.compile.{ Compilers, CompileAnalysis, CompileOptions, CompileOrder,
-  CompileResult, DefinesClass, IncOptionsUtil, Inputs, MiniSetup, PerClasspathEntryLookup,
-  PreviousResult, Setup, TransactionalManagerType }
-import sbt.internal.inc.{ AnalyzingCompiler, Analysis, CompilerCache, FileValueCache,
-  Locate, LoggerReporter, MixedAnalyzingCompiler, ScalaInstance, ClasspathOptionsUtil }
+import xsbti.compile.{
+  Compilers,
+  ClasspathOptions,
+  CompileAnalysis,
+  CompileOptions,
+  CompileOrder,
+  CompileResult,
+  DefinesClass,
+  IncOptions,
+  IncOptionsUtil,
+  Inputs,
+  MiniSetup,
+  PerClasspathEntryLookup,
+  PreviousResult,
+  Setup,
+  TransactionalManagerType
+}
+import sbt.internal.inc.{
+  AnalyzingCompiler,
+  Analysis,
+  ClassfileManager,
+  CompilerCache,
+  FileValueCache,
+  IncrementalCompilerImpl,
+  Locate,
+  LoggerReporter,
+  MixedAnalyzingCompiler,
+  ScalaInstance,
+  ClasspathOptionsUtil
+}
 
 object Defaults extends BuildCommon {
   final val CacheDirectoryName = "cache"
diff --git a/main/src/main/scala/sbt/Keys.scala b/main/src/main/scala/sbt/Keys.scala
index adc171250..6d37b03b2 100644
--- a/main/src/main/scala/sbt/Keys.scala
+++ b/main/src/main/scala/sbt/Keys.scala
@@ -7,9 +7,23 @@ import java.io.File
 import java.net.URL
 import scala.concurrent.duration.{ FiniteDuration, Duration }
 import Def.ScopedKey
-import sbt.internal.inc.ScalaInstance
-import xsbti.compile.{ DefinesClass, ClasspathOptions, CompileAnalysis, CompileOptions, CompileOrder,
-  Compilers, CompileResult, GlobalsCache, IncOptions, Inputs, PreviousResult, Setup }
+import sbt.internal.util.complete._
+import sbt.internal.inc.{ MixedAnalyzingCompiler, ScalaInstance }
+import std.TaskExtra._
+import xsbti.compile.{
+  DefinesClass,
+  ClasspathOptions,
+  CompileAnalysis,
+  CompileOptions,
+  CompileOrder,
+  Compilers,
+  CompileResult,
+  GlobalsCache,
+  IncOptions,
+  Inputs,
+  PreviousResult,
+  Setup
+}
 import scala.xml.{ Node => XNode, NodeSeq }
 import org.apache.ivy.core.module.{ descriptor, id }
 import descriptor.ModuleDescriptor, id.ModuleRevisionId
diff --git a/main/src/main/scala/sbt/Main.scala b/main/src/main/scala/sbt/Main.scala
index 6ad7f9b77..893ee2151 100644
--- a/main/src/main/scala/sbt/Main.scala
+++ b/main/src/main/scala/sbt/Main.scala
@@ -3,9 +3,24 @@
  */
 package sbt
 
-import sbt.internal.{ Act, Aggregation, BuildStructure, BuildUnit, CommandStrings, EvaluateConfigurations,
-  Inspect, IvyConsole, Load, LoadedBuildUnit, Output, PluginsDebug, ProjectNavigation, Script, SessionSettings,
-  SettingCompletions }
+import sbt.internal.{
+  Act,
+  Aggregation,
+  BuildStructure,
+  BuildUnit,
+  CommandStrings,
+  EvaluateConfigurations,
+  Inspect,
+  IvyConsole,
+  Load,
+  LoadedBuildUnit,
+  Output,
+  PluginsDebug,
+  ProjectNavigation,
+  Script,
+  SessionSettings,
+  SettingCompletions
+}
 import sbt.internal.util.{ AttributeKey, AttributeMap, complete, ConsoleOut, GlobalLogging, LineRange, MainLogging, SimpleReader, Types }
 import sbt.util.{ Level, Logger }
 
@@ -465,12 +480,13 @@ object BuiltinCommands {
       def ignoreMsg = if (Project.isProjectLoaded(s)) "using previously loaded project" else "no project loaded"
 
       result match {
-        case ""                     => retry
-        case _ if matches("retry")  => retry
-        case _ if matches(Quit)     => s.exit(ok = false)
-        case _ if matches("ignore") => s.log.warn(s"Ignoring load failure: $ignoreMsg.") ; s
-        case _ if matches("last")   => LastCommand :: loadProjectCommand(LoadFailed, loadArg) :: s
-        case _                      => println("Invalid response."); doLoadFailed(s, loadArg)
+        case ""                    => retry
+        case _ if matches("retry") => retry
+        case _ if matches(Quit)    => s.exit(ok = false)
+        case _ if matches("ignore") =>
+          s.log.warn(s"Ignoring load failure: $ignoreMsg."); s
+        case _ if matches("last") => LastCommand :: loadProjectCommand(LoadFailed, loadArg) :: s
+        case _                    => println("Invalid response."); doLoadFailed(s, loadArg)
       }
     }
 
diff --git a/project/Formatting.scala b/project/Formatting.scala
index ce6087a02..082e9bfda 100644
--- a/project/Formatting.scala
+++ b/project/Formatting.scala
@@ -1,16 +1,19 @@
 import sbt._
-import Keys._
-import com.typesafe.sbt.SbtScalariform.{ ScalariformKeys => sr, _ }
+import sbt.Keys._
+import com.typesafe.sbt.SbtScalariform._
+import ScalariformKeys.{ format => scalariformFormat, preferences => scalariformPreferences }
 
 object Formatting {
   lazy val BuildConfig = config("build") extend Compile
   lazy val BuildSbtConfig = config("buildsbt") extend Compile
 
+  val scalariformCheck = taskKey[Unit]("Checks that the existing code is formatted, via git diff")
+
   lazy val settings: Seq[Setting[_]] = Seq() ++ scalariformSettings ++ prefs
   lazy val prefs: Seq[Setting[_]] = {
     import scalariform.formatter.preferences._
     Seq(
-      sr.preferences := sr.preferences.value.setPreference(AlignSingleLineCaseStatements, true)
+      scalariformPreferences ~= (_.setPreference(AlignSingleLineCaseStatements, true))
     )
   }
   lazy val sbtFilesSettings: Seq[Setting[_]] = Seq() ++ scalariformSettings ++ prefs ++
@@ -19,12 +22,16 @@ object Formatting {
     Seq(
       scalaSource in BuildConfig := baseDirectory.value / "project",
       scalaSource in BuildSbtConfig := baseDirectory.value / "project",
-      includeFilter in (BuildConfig, sr.format) := ("*.scala": FileFilter),
-      includeFilter in (BuildSbtConfig, sr.format) := ("*.sbt": FileFilter),
-      sr.format in Compile := {
-        val x = (sr.format in BuildSbtConfig).value
-        val y = (sr.format in BuildConfig).value
-        (sr.format in Compile).value
+      includeFilter in (BuildConfig, scalariformFormat) := ("*.scala": FileFilter),
+      includeFilter in (BuildSbtConfig, scalariformFormat) := ("*.sbt": FileFilter),
+      scalariformFormat in Compile := {
+        val x = (scalariformFormat in BuildSbtConfig).value
+        val y = (scalariformFormat in BuildConfig).value
+        (scalariformFormat in Compile).value
+      },
+      scalariformCheck := {
+        val diff = "git diff".!!
+        if (diff.nonEmpty) sys.error("Working directory is dirty!\n" + diff)
       }
     )
 }