diff --git a/tool/update-deps b/tool/update-deps
index 66dc02087f..7710d4ae1b 100755
--- a/tool/update-deps
+++ b/tool/update-deps
@@ -246,6 +246,8 @@ end
 def read_make_deps(cwd)
   dependencies = {}
   make_p, make_p_stderr, make_p_status = Open3.capture3("make -p all miniruby ruby golf")
+  File.open('update-deps.make.out.log', 'w') {|f| f.print make_p }
+  File.open('update-deps.make.err.log', 'w') {|f| f.print make_p_stderr }
   if !make_p_status.success?
     puts make_p_stderr
     raise "make failed"