diff --git a/internal/util-cache/src/test/scala/FileInfoSpec.scala b/internal/util-cache/src/test/scala/FileInfoSpec.scala
new file mode 100644
index 000000000..974956bc4
--- /dev/null
+++ b/internal/util-cache/src/test/scala/FileInfoSpec.scala
@@ -0,0 +1,23 @@
+package sbt.internal.util
+
+import scala.json.ast.unsafe._
+import sjsonnew._, support.scalajson.unsafe._
+
+class FileInfoSpec extends UnitSpec {
+  val file = new java.io.File(".")
+  val fileInfo: ModifiedFileInfo = FileModified(file, file.lastModified())
+  val filesInfo = FilesInfo(Set(fileInfo))
+
+  it should "round trip" in assertRoundTrip(filesInfo)
+
+  def assertRoundTrip[A: JsonWriter: JsonReader](x: A) = {
+    val jsonString: String = toJsonString(x)
+    val jValue: JValue = Parser.parseUnsafe(jsonString)
+    val y: A = Converter.fromJson[A](jValue).get
+    assert(x === y)
+  }
+
+  def assertJsonString[A: JsonWriter](x: A, s: String) = assert(toJsonString(x) === s)
+
+  def toJsonString[A: JsonWriter](x: A): String = CompactPrinter(Converter.toJson(x).get)
+}