diff --git a/fcore/app-type.sml b/fcore/app-type.sml
index ed3ea76..ff3e5a7 100644
--- a/fcore/app-type.sml
+++ b/fcore/app-type.sml
@@ -1,34 +1,11 @@
-signature APP_TYPE =
-sig
-  datatype mode = NORMAL_MODE of string
-
-  type app_type =
-    { mode: mode
-    , buffer: LineGap.t
-    , searchList: SearchList.t
-    , searchString: string
-    , windowWidth: int
-    , windowHeight: int
-    (* line to start drawing from *)
-    , startLine: int
-    (* absolute index of movable cursor *)
-    , cursorIdx: int
-    (* msgs to send after an update.
-     * The list of messages is reset on each invocation of AppUpdate.update. *)
-    , msgs: MailboxType.t list
-
-    }
-
-  val init: LineGap.t * int * int -> app_type
-end
-
-structure AppType :> APP_TYPE =
+structure AppType =
 struct
   datatype mode = NORMAL_MODE of string
 
   type app_type =
     { mode: mode
     , buffer: LineGap.t
+    , bufferModifyTime: Time.time
     , searchList: SearchList.t
     , searchString: string
     , windowWidth: int
@@ -42,9 +19,10 @@ struct
     , msgs: MailboxType.t list
     }
 
-  fun init (buffer, windowWidth, windowHeight) : app_type =
+  fun init (buffer, windowWidth, windowHeight, time) : app_type =
     { mode = NORMAL_MODE ""
     , buffer = buffer
+    , bufferModifyTime = time
     , searchList = SearchList.empty
     , searchString = ""
     , windowWidth = windowWidth
diff --git a/shell/shell.sml b/shell/shell.sml
index 4766d54..2ca01c5 100644
--- a/shell/shell.sml
+++ b/shell/shell.sml
@@ -63,7 +63,7 @@ struct
       val io = TextIO.openIn "temp.txt"
       val lineGap = ioToLineGap (io, LineGap.empty)
       val _ = TextIO.closeIn io
-      val app = AppType.init (lineGap, 1920, 1080)
+      val app = AppType.init (lineGap, 1920, 1080, Time.now ())
 
       (* todo: remove temp line below which tests search list *)
       val app =