diff --git a/compile/interface/src/main/scala/xsbt/API.scala b/compile/interface/src/main/scala/xsbt/API.scala
index 8af37f6b0..e556590a5 100644
--- a/compile/interface/src/main/scala/xsbt/API.scala
+++ b/compile/interface/src/main/scala/xsbt/API.scala
@@ -22,16 +22,19 @@ final class API(val global: CallbackGlobal) extends Compat {
   @inline def debug(msg: => String) = if (settings.verbose.value) inform(msg)
 
   def newPhase(prev: Phase) = new ApiPhase(prev)
-  class ApiPhase(prev: Phase) extends Phase(prev) {
+  class ApiPhase(prev: Phase) extends GlobalPhase(prev) {
     override def description = "Extracts the public API from source files."
     def name = API.name
-    def run: Unit =
+    override def run(): Unit =
       {
         val start = System.currentTimeMillis
-        currentRun.units.foreach(processUnit)
+        super.run
         val stop = System.currentTimeMillis
         debug("API phase took : " + ((stop - start) / 1000.0) + " s")
       }
+
+    def apply(unit: global.CompilationUnit): Unit = processUnit(unit)
+
     def processUnit(unit: CompilationUnit) = if (!unit.isJava) processScalaUnit(unit)
     def processScalaUnit(unit: CompilationUnit): Unit = {
       val sourceFile = unit.source.file.file
diff --git a/compile/interface/src/main/scala/xsbt/Analyzer.scala b/compile/interface/src/main/scala/xsbt/Analyzer.scala
index 2bf01f630..adc26ff5e 100644
--- a/compile/interface/src/main/scala/xsbt/Analyzer.scala
+++ b/compile/interface/src/main/scala/xsbt/Analyzer.scala
@@ -19,11 +19,11 @@ final class Analyzer(val global: CallbackGlobal) extends LocateClassFile {
   import global._
 
   def newPhase(prev: Phase): Phase = new AnalyzerPhase(prev)
-  private class AnalyzerPhase(prev: Phase) extends Phase(prev) {
+  private class AnalyzerPhase(prev: Phase) extends GlobalPhase(prev) {
     override def description = "Finds concrete instances of provided superclasses, and application entry points."
     def name = Analyzer.name
-    def run {
-      for (unit <- currentRun.units if !unit.isJava) {
+    def apply(unit: CompilationUnit) {
+      if (!unit.isJava) {
         val sourceFile = unit.source.file.file
         // build list of generated classes
         for (iclass <- unit.icode) {
diff --git a/compile/interface/src/main/scala/xsbt/Dependency.scala b/compile/interface/src/main/scala/xsbt/Dependency.scala
index 80d68c5ba..edcc3bd0c 100644
--- a/compile/interface/src/main/scala/xsbt/Dependency.scala
+++ b/compile/interface/src/main/scala/xsbt/Dependency.scala
@@ -33,11 +33,11 @@ final class Dependency(val global: CallbackGlobal) extends LocateClassFile {
   import global._
 
   def newPhase(prev: Phase): Phase = new DependencyPhase(prev)
-  private class DependencyPhase(prev: Phase) extends Phase(prev) {
+  private class DependencyPhase(prev: Phase) extends GlobalPhase(prev) {
     override def description = "Extracts dependency information"
     def name = Dependency.name
-    def run: Unit = {
-      for (unit <- currentRun.units if !unit.isJava) {
+    def apply(unit: CompilationUnit): Unit = {
+      if (!unit.isJava) {
         // build dependencies structure
         val sourceFile = unit.source.file.file
         if (global.callback.nameHashing) {
diff --git a/sbt/src/sbt-test/api/source-path/build.sbt b/sbt/src/sbt-test/api/source-path/build.sbt
new file mode 100644
index 000000000..58e2a083c
--- /dev/null
+++ b/sbt/src/sbt-test/api/source-path/build.sbt
@@ -0,0 +1,5 @@
+scalaVersion := "2.11.7"
+
+scalacOptions in Compile ++= "-sourcepath" :: (baseDirectory.value / "srcpath").toString :: Nil
+
+
diff --git a/sbt/src/sbt-test/api/source-path/src/main/scala/test.scala b/sbt/src/sbt-test/api/source-path/src/main/scala/test.scala
new file mode 100644
index 000000000..18ca50b84
--- /dev/null
+++ b/sbt/src/sbt-test/api/source-path/src/main/scala/test.scala
@@ -0,0 +1,18 @@
+
+object Test {
+  // When the refchecks compiler phase checks if Tuple2 has the
+  // @deprecated annotation, it forces the info for the
+  // `@deprecatedInheritance` annotation (the only annotation on
+  // class Tuple2.
+  //
+  // Because we are compiling with `-sourcpath` that contains a
+  // source file for `deprecatedInheritance`, this triggers a
+  // `compileLate` of that file (which basically runs all previous
+  // compiler phases on that file.)
+  //
+  // `compileLate` assumes that all of the phases are subclasses
+  // of `GlobalPhase`, rather than just `Phase`. This triggers a
+  // `ClassCastException` when it encounters SBT's custom
+  // API phase.
+  new Tuple2("", "")
+}
diff --git a/sbt/src/sbt-test/api/source-path/srcpath/scala/deprecatedInheritance.scala b/sbt/src/sbt-test/api/source-path/srcpath/scala/deprecatedInheritance.scala
new file mode 100644
index 000000000..8f49314ca
--- /dev/null
+++ b/sbt/src/sbt-test/api/source-path/srcpath/scala/deprecatedInheritance.scala
@@ -0,0 +1,4 @@
+package scala
+
+private[scala] // for now, this needs to be generalized to communicate other modifier deltas
+class deprecatedInheritance(message: String = "", since: String = "") extends scala.annotation.StaticAnnotation
diff --git a/sbt/src/sbt-test/api/source-path/test b/sbt/src/sbt-test/api/source-path/test
new file mode 100644
index 000000000..5df2af1f3
--- /dev/null
+++ b/sbt/src/sbt-test/api/source-path/test
@@ -0,0 +1 @@
+> compile