diff --git a/lib/lyx2lyx/lyx_1_6.py b/lib/lyx2lyx/lyx_1_6.py
index 520ea6184a..224ceebf84 100644
--- a/lib/lyx2lyx/lyx_1_6.py
+++ b/lib/lyx2lyx/lyx_1_6.py
@@ -209,7 +209,7 @@ def extract_argument(line):
     return (line[:pos + 1], line[pos + 1:])
 
 
-def latex2ert(line):
+def latex2ert(line, isindex):
     '''Converts LaTeX commands into ERT. line may well be a multi-line
        string when it is returned.'''
     if not line:
@@ -246,6 +246,9 @@ def latex2ert(line):
     # put all remaining braces in ERT
     line = wrap_into_ert(line, '}', '}')
     line = wrap_into_ert(line, '{', '{')
+    if isindex:
+        # active character that is not available in all font encodings
+        line = wrap_into_ert(line, '|', '|')
     retval += line
     return retval
 
@@ -257,10 +260,12 @@ unicode_reps = read_unicodesymbols()
 #end up inside ERT. That routine could be modified so that it returned
 #a list of lines, and we could then skip ERT bits and only deal with
 #the other bits.
-def latex2lyx(data):
+def latex2lyx(data, isindex):
     '''Takes a string, possibly multi-line, and returns the result of
     converting LaTeX constructs into LyX constructs. Returns a list of
-    lines, suitable for insertion into document.body.'''
+    lines, suitable for insertion into document.body.
+    The bool isindex specifies whether we are in an index macro (which
+    has some specific active characters that need to be ERTed).'''
 
     if not data:
         return [""]
@@ -309,14 +314,14 @@ def latex2lyx(data):
             g = m.group(3)
             if s:
                 # this is non-math!
-                s = latex2ert(s)
+                s = latex2ert(s, isindex)
                 subst = s.split('\n')
                 retval += subst
             retval.append("\\begin_inset Formula " + f)
             retval.append("\\end_inset")
             m = mathre.match(g)
         # Handle whatever is left, which is just text
-        g = latex2ert(g)
+        g = latex2ert(g, isindex)
         subst = g.split('\n')
         retval += subst
     return retval
@@ -1097,7 +1102,7 @@ def convert_latexcommand_index(document):
             linelist = [""]
         else:
             fullcontent = m.group(1)
-            linelist = latex2lyx(fullcontent)
+            linelist = latex2lyx(fullcontent, True)
         #document.warning(fullcontent)
 
         linelist = ["\\begin_inset Index", "status collapsed", "\\begin_layout Standard", ""] + \
@@ -2177,7 +2182,7 @@ def convert_subfig(document):
         addedLines -= 1
         subst = ['\\begin_inset Float figure', 'wide false', 'sideways false',
                  'status open', '', '\\begin_layout Plain Layout', '\\begin_inset Caption',
-                 '', '\\begin_layout Plain Layout'] + latex2lyx(caption) + \
+                 '', '\\begin_layout Plain Layout'] + latex2lyx(caption, False) + \
                  [ '\\end_layout', '', '\\end_inset', '',
                  '\\end_layout', '', '\\begin_layout Plain Layout']
         document.body[i : i] = subst
diff --git a/src/OutputParams.cpp b/src/OutputParams.cpp
index 498c65148c..a4d60c698f 100644
--- a/src/OutputParams.cpp
+++ b/src/OutputParams.cpp
@@ -24,7 +24,8 @@ OutputParams::OutputParams(Encoding const * enc)
 	  use_japanese(false), linelen(0), depth(0),
 	  exportdata(new ExportData),
 	  inComment(false), inTableCell(NO), inFloat(NONFLOAT),
-	  inDeletedInset(0), changeOfDeletedInset(Change::UNCHANGED),
+	  inIndexEntry(false), inDeletedInset(0),
+	  changeOfDeletedInset(Change::UNCHANGED),
 	  par_begin(0), par_end(0), isLastPar(false),
 	  dryrun(false), verbatim(false)
 {
diff --git a/src/OutputParams.h b/src/OutputParams.h
index 00a1e11030..bce61bcc28 100644
--- a/src/OutputParams.h
+++ b/src/OutputParams.h
@@ -147,6 +147,11 @@ public:
 	 */
 	Float inFloat;
 
+	/** Whether we are inside an index inset.
+	 *  ERT needs to know this, due to the active chars.
+	 */
+	bool inIndexEntry;
+
 	/** Whether we are inside an inset that is logically deleted.
 	 *  A value > 0 indicates a deleted inset.
          */
diff --git a/src/insets/InsetERT.cpp b/src/insets/InsetERT.cpp
index 6fc51e11d8..fba6c1ecc7 100644
--- a/src/insets/InsetERT.cpp
+++ b/src/insets/InsetERT.cpp
@@ -25,6 +25,7 @@
 #include "Lexer.h"
 #include "LyXAction.h"
 #include "MetricsInfo.h"
+#include "OutputParams.h"
 #include "ParagraphParameters.h"
 #include "Paragraph.h"
 #include "TextClass.h"
@@ -75,9 +76,33 @@ int InsetERT::latex(odocstream & os, OutputParams const & op) const
 }
 
 
-int InsetERT::plaintext(odocstream &, OutputParams const &) const
+int InsetERT::plaintext(odocstream & os, OutputParams const & rp) const
 {
-	return 0; // do not output TeX code
+	if (!rp.inIndexEntry)
+		// do not output TeX code
+		return 0;
+
+	ParagraphList::const_iterator par = paragraphs().begin();
+	ParagraphList::const_iterator end = paragraphs().end();
+
+	while (par != end) {
+		pos_type siz = par->size();
+		for (pos_type i = 0; i < siz; ++i) {
+			char_type const c = par->getChar(i);
+			// output the active characters
+			switch (c) {
+			case '|':
+			case '!':
+			case '@':
+				os.put(c);
+				break;
+			default:
+				break;
+			}
+		}
+		++par;
+	}
+	return 0;
 }
 
 
diff --git a/src/insets/InsetIndex.cpp b/src/insets/InsetIndex.cpp
index 398281d2a2..54254c5b3b 100644
--- a/src/insets/InsetIndex.cpp
+++ b/src/insets/InsetIndex.cpp
@@ -48,8 +48,10 @@ InsetIndex::InsetIndex(Buffer const & buf)
 
 
 int InsetIndex::latex(odocstream & os,
-		      OutputParams const & runparams) const
+		      OutputParams const & runparams_in) const
 {
+	OutputParams runparams(runparams_in);
+	runparams.inIndexEntry = true;
 	os << "\\index";
 	os << '{';
 	int i = 0;
diff --git a/status.16x b/status.16x
index 7bddf7292c..0508940471 100644
--- a/status.16x
+++ b/status.16x
@@ -69,8 +69,12 @@ What's new
 
 - Do not unnecessarily enquote brackets in the LaTeX output (bug 5988).
 
-- Remove the last '//' in the output of multiline equations. This caused
+- Remove the last '\\' in the output of multiline equations. This caused
   labels to appear double (bug 2969).
+ 
+- Put "|" characters in index entries in ERT when converting old documents
+  to LyX 1.6.x format, to assure the character is treated verbatim
+  (bug 6179).
 
 
 * USER INTERFACE