diff --git a/developer_manual/conf.py b/developer_manual/conf.py
index 24623a67e..5acdcf4d2 100644
--- a/developer_manual/conf.py
+++ b/developer_manual/conf.py
@@ -182,7 +182,7 @@ latex_elements = {
 #'pointsize': '10pt',
 
 # Additional stuff for the LaTeX preamble.
-'preamble': '\extrafloats{100}\maxdeadcycles=500\DeclareUnicodeCharacter{274C}{\sffamily X}',
+'preamble': '\\extrafloats{100}\\maxdeadcycles=500\\DeclareUnicodeCharacter{274C}{\\sffamily X}',
 }
 
 # Grouping the document tree into LaTeX files. List of tuples