Index: ruby-1.8.6/Makefile.in
===================================================================
--- ruby-1.8.6.orig/Makefile.in	2007-07-16 15:10:57.000000000 +0200
+++ ruby-1.8.6/Makefile.in	2007-07-16 15:10:58.000000000 +0200
@@ -131,7 +131,7 @@
 		if RUBY_PLATFORM =~ /mswin|bccwin|mingw/; \
 		  class File; \
 		    remove_const :ALT_SEPARATOR; \
-		    ALT_SEPARATOR = "\\"; \
+		    ALT_SEPARATOR = "\\\\"; \
 		  end; \
 		end; \
 		' > $@