diff --git a/grader b/grader
--- a/grader
+++ b/grader
@@ -24,6 +24,9 @@
 end
 
 def log_file_name
+  if !File.exists?(config.log_dir)
+    raise "Log directory does not exist: #{config.log_dir}"
+  end
   config.log_dir + 
     "/#{GRADER_ENV}_#{config.grader_mode}.#{Process.pid}"
 end