diff --git a/lib/doc/UserGuide.lyx b/lib/doc/UserGuide.lyx
index dfe1fd97a6..cb74614ef1 100644
--- a/lib/doc/UserGuide.lyx
+++ b/lib/doc/UserGuide.lyx
@@ -1,5 +1,5 @@
 #LyX 2.0.0svn created this file. For more info see http://www.lyx.org/
-\lyxformat 371
+\lyxformat 370
 \begin_document
 \begin_header
 \textclass scrbook
@@ -93,7 +93,6 @@
 \use_geometry false
 \use_amsmath 1
 \use_esint 1
-\use_mhchem 1
 \cite_engine basic
 \use_bibtopic false
 \use_indices false