diff --git a/doc/config.rst b/doc/config.rst
index ec26d7b2f..da9892be9 100644
--- a/doc/config.rst
+++ b/doc/config.rst
@@ -1768,7 +1768,7 @@ These options influence LaTeX output. See further :doc:`latex`.
      ``'inputenc'``
         "inputenc" package inclusion, defaults to
         ``'\\usepackage[utf8]{inputenc}'`` when using pdflatex.
-        Otherwise unset.
+        Otherwise empty.
 
         .. versionchanged:: 1.4.3
            Previously ``'\\usepackage[utf8]{inputenc}'`` was used for all
diff --git a/sphinx/templates/latex/content.tex_t b/sphinx/templates/latex/content.tex_t
index 1581a5822..670a92f46 100644
--- a/sphinx/templates/latex/content.tex_t
+++ b/sphinx/templates/latex/content.tex_t
@@ -15,9 +15,7 @@
 \fi \sphinxpxdimen=<%= pxunit %>\relax
 <%= passoptionstopackages %>
 <%= geometry %>
-<% if latex_engine == 'pdflatex' -%>
 <%= inputenc %>
-<% endif -%>
 <%= utf8extra %>
 <%= cmappkg %>
 <%= fontenc %>
diff --git a/sphinx/writers/latex.py b/sphinx/writers/latex.py
index 90d7096cd..84697a4f9 100644
--- a/sphinx/writers/latex.py
+++ b/sphinx/writers/latex.py
@@ -102,7 +102,9 @@ DEFAULT_SETTINGS = {
 ADDITIONAL_SETTINGS = {
     'pdflatex': {
         'inputenc':     '\\usepackage[utf8]{inputenc}',
-        'utf8extra':    '\\DeclareUnicodeCharacter{00A0}{\\nobreakspace}',
+        'utf8extra':   ('\\ifdefined\\DeclareUnicodeCharacter\n'
+                        '  \\DeclareUnicodeCharacter{00A0}{\\nobreakspace}\n'
+                        '\\fi'),
     },
     'xelatex': {
         'latex_engine': 'xelatex',