diff --git a/documentation/Makefile b/documentation/Makefile
index 4d721d30f3..d40f390e2b 100644
--- a/documentation/Makefile
+++ b/documentation/Makefile
@@ -3,7 +3,7 @@
 
 # You can set these variables from the command line, and also
 # from the environment for the first two.
-SPHINXOPTS    ?=
+SPHINXOPTS    ?= -j auto
 SPHINXBUILD   ?= sphinx-build
 SOURCEDIR     = .
 BUILDDIR      = _build