diff --git a/ext/ripper/depend b/ext/ripper/depend
index 4f48512a41..f85d887a71 100644
--- a/ext/ripper/depend
+++ b/ext/ripper/depend
@@ -44,7 +44,7 @@ eventids2table.c: $(srcdir)/tools/generate.rb $(SRC2)
 preproc: ripper.E
 ripper.E: ripper.c
 	$(ECHO) preprocessing ripper.c
-	$(Q) $(CC) -E $(CPPFLAGS) ripper.c | $(RUBY) $(srcdir)/tools/strip.rb > $@
+	$(Q) $(CC) -E $(INCFLAGS) $(CPPFLAGS) $< | $(RUBY) $(srcdir)/tools/strip.rb > $@
 
 # AUTOGENERATED DEPENDENCIES START
 ripper.o: $(RUBY_EXTCONF_H)
diff --git a/ext/ripper/tools/strip.rb b/ext/ripper/tools/strip.rb
index 82022d0b55..0e409eb63b 100755
--- a/ext/ripper/tools/strip.rb
+++ b/ext/ripper/tools/strip.rb
@@ -1,11 +1,10 @@
 # frozen_string_literal: false
 last_is_void = false
 ARGF.each do |line|
-  if line.strip.empty?
-    #puts() unless last_is_void
+  case line
+  when /\A\s*\z/, /\A\#/
+    puts unless last_is_void
     last_is_void = true
-  elsif /\A\#/ === line
-    ;
   else
     print line
     last_is_void = false