diff --git a/common.mk b/common.mk
index 25937135d7..ded8e70c99 100644
--- a/common.mk
+++ b/common.mk
@@ -226,7 +226,7 @@ mjit_config.h: Makefile
 $(TIMESTAMPDIR)/$(MJIT_HEADER:.h=)$(MJIT_HEADER_SUFFIX).time: probes.h vm.$(OBJEXT) \
 		$(TIMESTAMPDIR)/$(arch)/.time $(srcdir)/tool/run_without_tabs.rb
 	$(ECHO) building $(@F:.time=.h)
-	$(Q) $(BASERUBY) $(srcdir)/tool/run_without_tabs.rb \
+	$(Q) $(BASERUBY) $(srcdir)/tool/run_without_tabs.rb $(MJIT_DEBUGFLAGS) -- \
 		$(CPP) -DMJIT_HEADER $(MJIT_HEADER_FLAGS) $(CFLAGS) $(XCFLAGS) $(CPPFLAGS) $(srcdir)/vm.c $(CPPOUTFLAG)$(@F:.time=.h).new
 	$(Q) $(IFCHANGE) "--timestamp=$@" $(@F:.time=.h) $(@F:.time=.h).new
 
diff --git a/tool/run_without_tabs.rb b/tool/run_without_tabs.rb
index cf27f099c7..aa5fb7f798 100644
--- a/tool/run_without_tabs.rb
+++ b/tool/run_without_tabs.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 # This is a script to run a command in ARGV, expanding tabs in some files
-# included by vm.c to normalize indentation of MJIT header.
+# included by vm.c to normalize indentation of MJIT header when debugflags
+# is -ggdb3 (default).
 #
 # Note that preprocessor of GCC converts a hard tab to one spaces, where
 # we expect it to be shown as 8 spaces. To obviate this script, we need
@@ -21,12 +22,18 @@ SKIPPED_FILES = %w[
   vm_opts.h
 ]
 
+unless split_index = ARGV.index('--')
+  abort "Usage: #{$0} [debugflags] -- [cmmand...]"
+end
+debugflags, command = ARGV[0...split_index], ARGV[(split_index + 1)..-1]
+
 srcdir = File.expand_path('..', __dir__)
 targets = EXPAND_TARGETS.flat_map { |t| Dir.glob(File.join(srcdir, t)) } - SKIPPED_FILES.map { |f| File.join(srcdir, f) }
 sources = {}
 mtimes = {}
 
 targets.each do |target|
+  next unless debugflags.include?('-ggdb3')
   unless File.writable?(target)
     puts "tool/run_without_tabs.rb: Skipping #{target.dump} as it's not writable."
     next
@@ -49,7 +56,7 @@ targets.each do |target|
   FileUtils.touch(target, mtime: mtimes[target])
 end
 
-result = system(*ARGV)
+result = system(*command)
 
 targets.each do |target|
   if sources.key?(target)