diff --git a/dll/mk_def.py b/dll/mk_def.py
index 6e9fe92ac..2d0822eb0 100644
--- a/dll/mk_def.py
+++ b/dll/mk_def.py
@@ -1,7 +1,8 @@
 import re
+import os
 
 pat1 = re.compile(".*Z3_API.*")
-api = open('..\lib\z3_api.h', 'r')
+api = open('..%slib%sz3_api.h' % (os.sep, os.sep), 'r')
 
 z3def = open('z3.def', 'w')
 z3dbgdef = open('z3_dbg.def', 'w')
diff --git a/lib/api.py b/lib/api.py
index 61d176197..1382a9a18 100644
--- a/lib/api.py
+++ b/lib/api.py
@@ -22,8 +22,8 @@ from sets import Set
 log_h   = open('api_log_macros.h', 'w')
 log_c   = open('api_log_macros.cpp', 'w')
 exe_c   = open('api_commands.cpp', 'w')
-core_py = open('..\\python\\z3core.py', 'w')
-dotnet_fileout = '..\\Microsoft.Z3\\Native.cs'
+core_py = open('..%spython%sz3core.py' % (os.sep, os.sep), 'w')
+dotnet_fileout = '..%sMicrosoft.Z3%sNative.cs' % (os.sep, os.sep)
 ##
 log_h.write('// Automatically generated file, generator: api.py\n')
 log_h.write('#include\"z3.h\"\n')
diff --git a/python/mk_z3consts.py b/python/mk_z3consts.py
index 8f26317a0..35f6839c2 100644
--- a/python/mk_z3consts.py
+++ b/python/mk_z3consts.py
@@ -6,6 +6,7 @@
 # Author: Leonardo de Moura (leonardo)
 ############################################
 import re
+import os 
 
 blank_pat      = re.compile("^ *$")
 comment_pat    = re.compile("^ *//.*$")
@@ -14,7 +15,7 @@ typedef2_pat   = re.compile("typedef enum { *")
 openbrace_pat  = re.compile("{ *")
 closebrace_pat = re.compile("}.*;")
 
-api = open('..\\lib\\z3_api.h', 'r')
+api = open('..%slib%sz3_api.h' % (os.sep, os.sep), 'r')
 
 z3consts  = open('z3consts.py', 'w')
 z3consts.write('# Automatically generated file, generator: mk_z3consts.py\n\n')
diff --git a/python/mk_z3tactics.py b/python/mk_z3tactics.py
index c984c8a9f..9773697b9 100644
--- a/python/mk_z3tactics.py
+++ b/python/mk_z3tactics.py
@@ -6,11 +6,12 @@
 # Author: Leonardo de Moura (leonardo)
 ############################################
 import re
+import os
 
 tactic_pat  = re.compile("^[ \t]*ADD_TACTIC_CMD")
 probe_pat   = re.compile("^[ \t]*ADD_PROBE")
 
-cppfile = open('..\\lib\\install_tactics.cpp', 'r')
+cppfile = open('..%slib%sinstall_tactics.cpp' % (os.sep, os.sep), 'r')
 
 z3tactics  = open('z3tactics.py', 'w')
 z3tactics.write('# Automatically generated file, generator: mk_z3tactics.py\n')