diff --git a/main-actions/src/main/scala/sbt/Compiler.scala b/main-actions/src/main/scala/sbt/Compiler.scala
index 5332da9f9..f74df8e9a 100644
--- a/main-actions/src/main/scala/sbt/Compiler.scala
+++ b/main-actions/src/main/scala/sbt/Compiler.scala
@@ -8,7 +8,6 @@ import sbt.internal.inc.{ Analysis, AnalyzingCompiler, ClasspathOptions, Compile
 import xsbti.{ Logger => _, _ }
 import xsbti.compile.{ CompileOrder, Compilers, CompileResult, GlobalsCache, IncOptions, Inputs, MiniSetup }
 import CompileOrder.{ JavaThenScala, Mixed, ScalaThenJava }
-import Locate.DefinesClass
 import java.io.File
 
 import sbt.internal.librarymanagement.{ ComponentManager, IvyConfiguration }
diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 5913f0e5a..1397a4ff6 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -11,6 +11,7 @@ import Scope.{ fillTaskAxis, GlobalScope, ThisScope }
 import sbt.internal.librarymanagement.mavenint.{ PomExtraDependencyAttributes, SbtPomExtraProperties }
 import xsbt.api.Discovery
 import xsbti.compile.{ CompileAnalysis, CompileOptions, CompileOrder, CompileResult, DefinesClass, IncOptions, IncOptionsUtil, Inputs, MiniSetup, PreviousResult, Setup, TransactionalManagerType }
+import xsbti.compile.PerClasspathEntryLookup
 import Project.{ inConfig, inScope, inTask, richInitialize, richInitializeTask, richTaskSessionVar }
 import Def.{ Initialize, ScopedKey, Setting, SettingsDefinition }
 import sbt.internal.librarymanagement.{ CustomPomParser, DependencyFilter }
@@ -88,7 +89,7 @@ object Defaults extends BuildCommon {
       apiMappings := Map.empty,
       autoScalaLibrary :== true,
       managedScalaInstance :== true,
-      definesClass :== FileValueCache(Locate.definesClass _).get,
+      classpathEntryDefinesClass :== FileValueCache(Locate.definesClass _).get,
       traceLevel in run :== 0,
       traceLevel in runMain :== 0,
       traceLevel in console :== Int.MaxValue,
@@ -886,13 +887,17 @@ object Defaults extends BuildCommon {
       finally x.close() // workaround for #937
     }
   def compileIncSetupTask = Def.task {
-    val dc: File => DefinesClass = {
-      val dc = definesClass.value
-      f => new DefinesClass { override def apply(className: String): Boolean = dc(f)(className) }
+    val lookup = new PerClasspathEntryLookup {
+      private val cachedAnalysisMap = analysisMap(dependencyClasspath.value)
+      private val cachedPerEntryDefinesClassLookup = Keys.classpathEntryDefinesClass.value
+
+      override def analysis(classpathEntry: File): Maybe[CompileAnalysis] =
+        o2m(cachedAnalysisMap(classpathEntry))
+      override def definesClass(classpathEntry: File): DefinesClass =
+        cachedPerEntryDefinesClassLookup(classpathEntry)
     }
     new Setup(
-      f1(t => o2m(analysisMap(dependencyClasspath.value)(t))),
-      f1(dc),
+      lookup,
       (skip in compile).value,
       // TODO - this is kind of a bad way to grab the cache directory for streams...
       streams.value.cacheDirectory / compileAnalysisFilename.value,
diff --git a/main/src/main/scala/sbt/Keys.scala b/main/src/main/scala/sbt/Keys.scala
index 2e214701b..c032ac778 100644
--- a/main/src/main/scala/sbt/Keys.scala
+++ b/main/src/main/scala/sbt/Keys.scala
@@ -8,7 +8,7 @@ import java.net.URL
 import scala.concurrent.duration.{ FiniteDuration, Duration }
 import Def.ScopedKey
 import sbt.internal.util.complete._
-import sbt.internal.inc.Locate.DefinesClass
+import xsbti.compile.DefinesClass
 import sbt.internal.inc.{ ClasspathOptions, MixedAnalyzingCompiler, ScalaInstance }
 import std.TaskExtra._
 import xsbti.compile.{ CompileAnalysis, CompileOptions, CompileOrder, Compilers, CompileResult, GlobalsCache, IncOptions, Inputs, PreviousResult, Setup }
@@ -195,7 +195,7 @@ object Keys {
   val compileIncSetup = TaskKey[Setup]("inc-compile-setup", "Configures aspects of incremental compilation.", DTask)
   val compilerCache = TaskKey[GlobalsCache]("compiler-cache", "Cache of scala.tools.nsc.Global instances.  This should typically be cached so that it isn't recreated every task run.", DTask)
   val stateCompilerCache = AttributeKey[GlobalsCache]("compiler-cache", "Internal use: Global cache.")
-  val definesClass = TaskKey[DefinesClass]("defines-class", "Internal use: provides a function that determines whether the provided file contains a given class.", Invisible)
+  val classpathEntryDefinesClass = TaskKey[File => DefinesClass]("classpath-entry-defines-class", "Internal use: provides a function that determines whether the provided file contains a given class.", Invisible)
   val doc = TaskKey[File]("doc", "Generates API documentation.", AMinusTask)
   val copyResources = TaskKey[Seq[(File, File)]]("copy-resources", "Copies resources to the output directory.", AMinusTask)
   val aggregate = SettingKey[Boolean]("aggregate", "Configures task aggregation.", BMinusSetting)