diff --git a/main/Build.scala b/main/Build.scala
index 0ac1d0377..295faab1b 100644
--- a/main/Build.scala
+++ b/main/Build.scala
@@ -135,12 +135,12 @@ object Index
 	}
 	def stringToKeyMap(settings: Settings[Scope]): Map[String, AttributeKey[_]] =
 	{
-		val multiMap = settings.data.values.flatMap(_.keys).toList.distinct.groupBy(_.label)
-		val duplicates = multiMap collect { case (k, x1 :: x2 :: _) => k }
+		val multiMap = settings.data.values.flatMap(_.keys).toSet[AttributeKey[_]].groupBy(_.label)
+		val duplicates = multiMap collect { case (k, xs) if xs.size > 1 => (k, xs.map(_.manifest)) } collect { case (k, xs) if xs.size > 1 => (k, xs) }
 		if(duplicates.isEmpty)
 			multiMap.collect { case (k, v) if validID(k) => (k, v.head) } toMap;
 		else
-			error(duplicates.mkString("AttributeKey ID collisions detected for '", "', '", "'"))
+			error(duplicates map { case (k, tps) => "'" + k + "' (" + tps.mkString(", ") + ")" } mkString("AttributeKey ID collisions detected for: ", ", ", ""))
 	}
 	private[this] type TriggerMap = collection.mutable.HashMap[Task[_], Seq[Task[_]]]
 	def triggers(ss: Settings[Scope]): Triggers[Task] =
diff --git a/main/Keys.scala b/main/Keys.scala
index 2dab01ab8..2216d9322 100644
--- a/main/Keys.scala
+++ b/main/Keys.scala
@@ -267,7 +267,7 @@ object Keys
 	type Streams = std.Streams[ScopedKey[_]]
 	type TaskStreams = std.TaskStreams[ScopedKey[_]]
 
-	def dummy[T](name: String, description: String): (TaskKey[T], Task[T]) = (TaskKey[T](name, description), dummyTask(name))
+	def dummy[T: Manifest](name: String, description: String): (TaskKey[T], Task[T]) = (TaskKey[T](name, description), dummyTask(name))
 	def dummyTask[T](name: String): Task[T] =
 	{
 		val base: Task[T] = task( error("Dummy task '" + name + "' did not get converted to a full task.") ) named name
diff --git a/main/Structure.scala b/main/Structure.scala
index c15379f6a..9f1d64e8e 100644
--- a/main/Structure.scala
+++ b/main/Structure.scala
@@ -530,10 +530,10 @@ object Scoped
 
 object InputKey
 {
-	def apply[T](label: String, description: String = ""): InputKey[T] =
+	def apply[T: Manifest](label: String, description: String = ""): InputKey[T] =
 		apply( AttributeKey[InputTask[T]](label, description) )
 
-	def apply[T](label: String, description: String, extend1: Scoped, extendN: Scoped*): InputKey[T] =
+	def apply[T: Manifest](label: String, description: String, extend1: Scoped, extendN: Scoped*): InputKey[T] =
 		apply( AttributeKey[InputTask[T]](label, description, extendScoped(extend1, extendN)) )
 
 	def apply[T](akey: AttributeKey[InputTask[T]]): InputKey[T] =
@@ -541,10 +541,10 @@ object InputKey
 }
 object TaskKey
 {
-	def apply[T](label: String, description: String = ""): TaskKey[T] =
+	def apply[T: Manifest](label: String, description: String = ""): TaskKey[T] =
 		apply( AttributeKey[Task[T]](label, description) )
 
-	def apply[T](label: String, description: String, extend1: Scoped, extendN: Scoped*): TaskKey[T] =
+	def apply[T: Manifest](label: String, description: String, extend1: Scoped, extendN: Scoped*): TaskKey[T] =
 		apply( AttributeKey[Task[T]](label, description, extendScoped(extend1, extendN)) )
 
 	def apply[T](akey: AttributeKey[Task[T]]): TaskKey[T] =
@@ -552,10 +552,10 @@ object TaskKey
 }
 object SettingKey
 {
-	def apply[T](label: String, description: String = ""): SettingKey[T] =
+	def apply[T: Manifest](label: String, description: String = ""): SettingKey[T] =
 		apply( AttributeKey[T](label, description) )
 
-	def apply[T](label: String, description: String, extend1: Scoped, extendN: Scoped*): SettingKey[T] =
+	def apply[T: Manifest](label: String, description: String, extend1: Scoped, extendN: Scoped*): SettingKey[T] =
 		apply( AttributeKey[T](label, description, extendScoped(extend1, extendN)) )
 
 	def apply[T](akey: AttributeKey[T]): SettingKey[T] =
diff --git a/util/collection/Attributes.scala b/util/collection/Attributes.scala
index 1025c03df..2302d326d 100644
--- a/util/collection/Attributes.scala
+++ b/util/collection/Attributes.scala
@@ -4,29 +4,39 @@
 package sbt
 
 import Types._
+import scala.reflect.Manifest
 
 // T must be invariant to work properly.
 //  Because it is sealed and the only instances go through AttributeKey.apply,
 //  a single AttributeKey instance cannot conform to AttributeKey[T] for different Ts
 sealed trait AttributeKey[T] {
+	def manifest: Manifest[T]
 	def label: String
 	def description: Option[String]
 	def extend: Seq[AttributeKey[_]]
 	override final def toString = label
+	override final def hashCode = label.hashCode
+	override final def equals(o: Any) = (this eq o.asInstanceOf[AnyRef]) || (o match {
+		case a: AttributeKey[t] => a.label == this.label && a.manifest == this.manifest
+		case _ => false
+	})
 }
 object AttributeKey
 {
-	def apply[T](name: String): AttributeKey[T] = new AttributeKey[T] {
+	def apply[T](name: String)(implicit mf: Manifest[T]): AttributeKey[T] = new AttributeKey[T] {
+		def manifest = mf
 		def label = name
 		def description = None
 		def extend = Nil
 	}
-	def apply[T](name: String, description0: String): AttributeKey[T] = new AttributeKey[T] {
+	def apply[T](name: String, description0: String)(implicit mf: Manifest[T]): AttributeKey[T] = new AttributeKey[T] {
+		def manifest = mf
 		def label = name
 		def description = Some(description0)
 		def extend = Nil
 	}
-	def apply[T](name: String, description0: String, extend0: Seq[AttributeKey[_]]): AttributeKey[T] = new AttributeKey[T] {
+	def apply[T](name: String, description0: String, extend0: Seq[AttributeKey[_]])(implicit mf: Manifest[T]): AttributeKey[T] = new AttributeKey[T] {
+		def manifest = mf
 		def label = name
 		def description = Some(description0)
 		def extend = extend0