diff --git a/pintos-env/pintos/userprog/process.c b/pintos-env/pintos/userprog/process.c
index dd5194e..e90620e 100755
--- a/pintos-env/pintos/userprog/process.c
+++ b/pintos-env/pintos/userprog/process.c
@@ -59,6 +59,12 @@ process_execute (const char *file_name)
   }
   strlcpy(program_name, file_name, i+1);
 
+  struct file* f = filesys_open (program_name);
+  if (f == NULL) {
+    return TID_ERROR;
+  }
+  file_close(f);
+
   /* Create a new thread to execute FILE_NAME. */
   tid = thread_create (program_name, PRI_DEFAULT, start_process, fn_copy);
   if (tid == TID_ERROR)