diff --git a/lib/lyx2lyx/lyx_1_5.py b/lib/lyx2lyx/lyx_1_5.py
index 77c80b242e..762d92be4d 100644
--- a/lib/lyx2lyx/lyx_1_5.py
+++ b/lib/lyx2lyx/lyx_1_5.py
@@ -653,17 +653,17 @@ def convert_commandparams(document):
             if commandparams_info[name][0] == "":
                 document.warning("Ignoring invalid option `%s' of command `%s'." % (option1, name))
             else:
-                lines.append('%s "%s"' % (commandparams_info[name][0], option1.replace('"', '\\"')))
+                lines.append('%s "%s"' % (commandparams_info[name][0], option1.replace('\\', '\\\\').replace('"', '\\"')))
         if option2 != "":
             if commandparams_info[name][1] == "":
                 document.warning("Ignoring invalid second option `%s' of command `%s'." % (option2, name))
             else:
-                lines.append('%s "%s"' % (commandparams_info[name][1], option2.replace('"', '\\"')))
+                lines.append('%s "%s"' % (commandparams_info[name][1], option2.replace('\\', '\\\\').replace('"', '\\"')))
         if argument != "":
             if commandparams_info[name][2] == "":
                 document.warning("Ignoring invalid argument `%s' of command `%s'." % (argument, name))
             else:
-                lines.append('%s "%s"' % (commandparams_info[name][2], argument.replace('"', '\\"')))
+                lines.append('%s "%s"' % (commandparams_info[name][2], argument.replace('\\', '\\\\').replace('"', '\\"')))
         document.body[i:i+1] = lines
         i = i + 1
 
@@ -690,13 +690,13 @@ def revert_commandparams(document):
                     preview_line = document.body[k]
                 elif (commandparams_info[name][0] != "" and
                       pname == commandparams_info[name][0]):
-                    option1 = pvalue.strip('"').replace('\\"', '"')
+                    option1 = pvalue.strip('"').replace('\\"', '"').replace('\\\\', '\\')
                 elif (commandparams_info[name][1] != "" and
                       pname == commandparams_info[name][1]):
-                    option2 = pvalue.strip('"').replace('\\"', '"')
+                    option2 = pvalue.strip('"').replace('\\"', '"').replace('\\\\', '\\')
                 elif (commandparams_info[name][2] != "" and
                       pname == commandparams_info[name][2]):
-                    argument = pvalue.strip('"').replace('\\"', '"')
+                    argument = pvalue.strip('"').replace('\\"', '"').replace('\\\\', '\\')
             elif document.body[k].strip() != "":
                 document.warning("Ignoring unknown contents `%s' in command inset %s." % (document.body[k], name))
         if name == "bibitem":
diff --git a/status.15x b/status.15x
index 3d5da6a115..5c13482e14 100644
--- a/status.15x
+++ b/status.15x
@@ -98,6 +98,9 @@ What's new
 - Fix a crash when exporting a file with a branch from the command line
   (bug 4255).
 
+- Fix a crash when importing an older LyX file (version < 1.5.0) that
+  contains index entries with escaped umlauts (bug 4333).
+
 - Exit gracefully and give the user some information if LyX catches an
   exception from an external program, such as iconv (part of bug 4385).