diff --git a/src/main/scala/io/findify/s3mock/provider/FileProvider.scala b/src/main/scala/io/findify/s3mock/provider/FileProvider.scala
index 81527d0..b0ac29f 100644
--- a/src/main/scala/io/findify/s3mock/provider/FileProvider.scala
+++ b/src/main/scala/io/findify/s3mock/provider/FileProvider.scala
@@ -46,7 +46,7 @@ class FileProvider(dir:String) extends Provider with LazyLogging {
     val files = bucketFiles.map(f => {Content(f.toString.drop(bucketFileString.length+1).dropWhile(_ == '/'), DateTime(f.lastModifiedTime.toEpochMilli), "0", f.size, "STANDARD")}).toList
     logger.debug(s"listing bucket contents: ${files.map(_.key)}")
     val commonPrefixes = delimiter match {
-      case Some(del) => files.flatMap(f => commonPrefix(f.key, prefixNoLeadingSlash, del)).distinct
+      case Some(del) => files.flatMap(f => commonPrefix(f.key, prefixNoLeadingSlash, del)).distinct.sorted
       case None => Nil
     }
     val filteredFiles = files.filterNot(f => commonPrefixes.exists(p => f.key.startsWith(p)))
diff --git a/src/test/scala/io/findify/s3mock/ListBucketTest.scala b/src/test/scala/io/findify/s3mock/ListBucketTest.scala
index f03bcba..74396da 100644
--- a/src/test/scala/io/findify/s3mock/ListBucketTest.scala
+++ b/src/test/scala/io/findify/s3mock/ListBucketTest.scala
@@ -154,14 +154,14 @@ class ListBucketTest extends S3MockTest {
       s3.putObject("list7", "dev/40/2017/03/13/00/_SUCCESS", "xxx")
       s3.putObject("list7", "dev/40/2017/03/13/01/_SUCCESS", "xxx")
       s3.putObject("list7", "dev/50/2017/03/13/00/_SUCCESS", "xxx")
-      s3.putObject("list7", "dev/60/2017/03/13/01/_SUCCESS", "xxx")
+      s3.putObject("list7", "dev/50/2017/03/13/01/_SUCCESS", "xxx")
       val req2 = new ListObjectsRequest()
       req2.setBucketName("list7")
       req2.setDelimiter("/")
       req2.setPrefix("dev/")
       val list2 = s3.listObjects(req2)
       val summaries2 = list2.getObjectSummaries.map(_.getKey).toList
-      list2.getCommonPrefixes.asScala.toList shouldBe List("dev/10", "dev/20", "dev/30", "dev/40", "dev/50")
+      list2.getCommonPrefixes.asScala.toList shouldBe List("dev/10/", "dev/20/", "dev/30/", "dev/40/", "dev/50/")
       summaries2 shouldBe Nil
     }
   }