diff --git a/sphinx/writers/latex.py b/sphinx/writers/latex.py
index 42b2db0ca..94384ad68 100644
--- a/sphinx/writers/latex.py
+++ b/sphinx/writers/latex.py
@@ -102,8 +102,9 @@ ADDITIONAL_SETTINGS = {
     'pdflatex': {
         'inputenc':     '\\usepackage[utf8]{inputenc}',
         'utf8extra':   ('\\ifdefined\\DeclareUnicodeCharacter\n'
+                        ' \\ifdefined\\DeclareUnicodeCharacterAsOptional\\else\n'
                         '  \\DeclareUnicodeCharacter{00A0}{\\nobreakspace}\n'
-                        '\\fi'),
+                        '\\fi\\fi'),
     },
     'xelatex': {
         'latex_engine': 'xelatex',