diff --git a/Source/appfat.cpp b/Source/appfat.cpp
index bdcd83e66..6329ef811 100644
--- a/Source/appfat.cpp
+++ b/Source/appfat.cpp
@@ -14,7 +14,7 @@ char sz_error_buf[256];
 /** Set to true when a fatal error is encountered and the application should shut down. */
 BOOL terminating;
 /** Thread id of the last callee to FreeDlg(). */
-int cleanup_thread_id;
+SDL_threadID cleanup_thread_id;
 
 /**
  * @brief Terminates the game and displays an error message box.
diff --git a/Source/appfat.h b/Source/appfat.h
index f7d06af05..83621607c 100644
--- a/Source/appfat.h
+++ b/Source/appfat.h
@@ -14,7 +14,6 @@ extern "C" {
 
 extern char sz_error_buf[256];
 extern BOOL terminating;
-extern int cleanup_thread_id;
 
 void TriggerBreak();
 char *GetErrorStr(DWORD error_code);