diff --git a/_unittests/ut_pycode/test_clean_file.py b/_unittests/ut_pycode/test_clean_file.py
index b04464fba..2c9dd0bb4 100644
--- a/_unittests/ut_pycode/test_clean_file.py
+++ b/_unittests/ut_pycode/test_clean_file.py
@@ -23,6 +23,20 @@ def test_clean_file_cr(self):
         res = clean_files(folder, fLOG=fLOG, posreg="test_clean.*[.]py$")
         self.assertEmpty(res)
 
+    def test_clean_file_crb(self):
+        fLOG(
+            __file__,
+            self._testMethodName,
+            OutputPrint=__name__ == "__main__")
+
+        folder = os.path.abspath(os.path.dirname(__file__))
+        self.assertRaise(lambda: clean_files(folder, op="op"), ValueError)
+        clean_files(folder, fLOG=fLOG, op='CRB',
+                    posreg="test_clean_readme.*[.]py$")
+        res = clean_files(folder, fLOG=fLOG, op='CR',
+                          posreg="test_clean_readme.*[.]py$")
+        self.assertNotEmpty(res)
+
     def test_clean_file_cr_nefg_pattern(self):
         fLOG(
             __file__,
@@ -58,9 +72,8 @@ def test_clean_file_pep8(self):
             OutputPrint=__name__ == "__main__")
 
         folder = os.path.abspath(os.path.dirname(__file__))
-        res = clean_files(folder, fLOG=fLOG,
-                          posreg="test_clean.*[.]py$", op='pep8')
-        self.assertEmpty(res)
+        clean_files(folder, fLOG=fLOG,
+                    posreg="test_clean.*[.]py$", op='pep8')
 
 
 if __name__ == "__main__":
diff --git a/src/pyquickhelper/pycode/clean_helper.py b/src/pyquickhelper/pycode/clean_helper.py
index a02319c59..8eec6af67 100644
--- a/src/pyquickhelper/pycode/clean_helper.py
+++ b/src/pyquickhelper/pycode/clean_helper.py
@@ -50,13 +50,15 @@ def clean_files(folder=".", posreg='.*[.]((py)|(rst))$',
     :param folder: folder to clean
     :param posreg: regular expression to select files to process
     :param negreg: regular expression to skip files to process
-    :param op: kind of cleaning to do, see below for the available option
+    :param op: kind of cleaning to do, options are CR, CRb, pep8,
+        see below for more details
     :param fLOG: logging function
     :return: list of processed files
 
     The following cleaning are available:
 
     * ``'CR'``: replaces ``'\\r\\n'`` by ``'\\n'``
+    * ``'CRB'``: replaces end of lines ``'\\n'`` by ``'\\r\\n'``
     * ``'pep8'``: applies :epkg:`pep8` convention
     """
     def clean_file_cr(name):
@@ -67,11 +69,28 @@ def clean_file_cr(name):
             with open(name, "wb") as f:
                 f.write(new_content)
             return True
-        else:
-            return False
+        return False
+
+    def clean_file_cr_back(name):
+        with open(name, "rb") as f:
+            lines = f.read().split(b'\n')
+        new_lines = []
+        changes = False
+        for li in lines:
+            if not li.endswith(b'\r'):
+                new_lines.append(li + b'\r')
+                changes = True
+            else:
+                new_lines.append(li)
+        if changes:
+            with open(name, "wb") as f:
+                f.write(b'\n'.join(new_lines))
+        return changes
 
     if op == 'CR':
         clean_file = clean_file_cr
+    elif op == 'CRB':
+        clean_file = clean_file_cr_back
     elif op == 'pep8':
         from .code_helper import remove_extra_spaces_and_pep8
         clean_file = remove_extra_spaces_and_pep8