diff --git a/main/src/main/scala/sbt/internal/Act.scala b/main/src/main/scala/sbt/internal/Act.scala
index ca12939a4..f3da90b61 100644
--- a/main/src/main/scala/sbt/internal/Act.scala
+++ b/main/src/main/scala/sbt/internal/Act.scala
@@ -49,12 +49,22 @@ object Act {
           new ParsedKey(makeScopedKey(proj, conf, task, extra, key), mask)
         }
 
-      for {
-        rawProject <- optProjectRef(index, current)
-        proj = resolveProject(rawProject, current)
-        confAmb <- config(index configs proj)
-        partialMask = ScopeMask(rawProject.isExplicit, confAmb.isExplicit, false, false)
-      } yield taskKeyExtra(proj, confAmb, partialMask)
+      val projectKeys =
+        for {
+          rawProject <- optProjectRef(index, current)
+          proj = resolveProject(rawProject, current)
+          confAmb <- config(index configs proj)
+          partialMask = ScopeMask(rawProject.isExplicit, confAmb.isExplicit, false, false)
+        } yield taskKeyExtra(proj, confAmb, partialMask)
+
+      val build = Some(BuildRef(current.build))
+      val buildKeys =
+        for {
+          confAmb <- config(index configs build)
+          partialMask = ScopeMask(false, confAmb.isExplicit, false, false)
+        } yield taskKeyExtra(build, confAmb, partialMask)
+
+      buildKeys combinedWith projectKeys map (_.flatten)
     }
   def makeScopedKey(proj: Option[ResolvedReference], conf: Option[String], task: Option[AttributeKey[_]], extra: ScopeAxis[AttributeMap], key: AttributeKey[_]): ScopedKey[_] =
     ScopedKey(Scope(toAxis(proj, Global), toAxis(conf map ConfigKey.apply, Global), toAxis(task, Global), extra), key)
@@ -68,11 +78,16 @@ object Act {
       selectFromValid(ss filter isValid(data), default)
     }
   def selectFromValid(ss: Seq[ParsedKey], default: Parser[ParsedKey])(implicit show: Show[ScopedKey[_]]): Parser[ParsedKey] =
-    selectByTask(selectByConfig(ss)) match {
-      case Seq()       => default
-      case Seq(single) => success(single)
-      case multi       => failure("Ambiguous keys: " + showAmbiguous(keys(multi)))
+    selectByTask(selectByConfig(ss)) partition isBuildKey match {
+      case (_, Seq(single))         => success(single)
+      case (Seq(single), Seq())     => success(single)
+      case (Seq(), Seq())           => default
+      case (buildKeys, projectKeys) => failure("Ambiguous keys: " + showAmbiguous(keys(buildKeys ++ projectKeys)))
     }
+  private def isBuildKey(parsed: ParsedKey): Boolean = parsed.key.scope.project match {
+    case Select(_: BuildReference) => true
+    case _                         => false
+  }
   private[this] def keys(ss: Seq[ParsedKey]): Seq[ScopedKey[_]] = ss.map(_.key)
   def selectByConfig(ss: Seq[ParsedKey]): Seq[ParsedKey] =
     ss match {
diff --git a/main/src/test/scala/ParseKey.scala b/main/src/test/scala/ParseKey.scala
index cc41901a7..147b54bf2 100644
--- a/main/src/test/scala/ParseKey.scala
+++ b/main/src/test/scala/ParseKey.scala
@@ -31,7 +31,7 @@ object ParseKey extends Properties("Key parser test") {
         parseExpected(structure, string, expected, mask)
     }
 
-  property("An unspecified project axis resolves to the current project") =
+  property("An unspecified project axis resolves to the current project or the build of the current project") =
     forAllNoShrink(structureDefinedKey) { (skm: StructureKeyMask) =>
       import skm.{ structure, key }
 
@@ -43,7 +43,7 @@ object ParseKey extends Properties("Key parser test") {
         ("Current: " + structure.current) |:
         parse(structure, string) {
           case Left(err) => false
-          case Right(sk) => sk.scope.project == Select(structure.current)
+          case Right(sk) => sk.scope.project == Select(structure.current) || sk.scope.project == Select(BuildRef(structure.current.build))
         }
     }
 
diff --git a/sbt/src/sbt-test/project/build-level-keys/test b/sbt/src/sbt-test/project/build-level-keys/test
new file mode 100644
index 000000000..a04b77809
--- /dev/null
+++ b/sbt/src/sbt-test/project/build-level-keys/test
@@ -0,0 +1,4 @@
+> baseDirectory
+
+> {.}/baseDirectory
+