diff --git a/docs/Makefile b/docs/Makefile
index 421d4f7d..b20dc238 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -2,7 +2,7 @@
 #
 
 # You can set these variables from the command line.
-SPHINXOPTS    =
+SPHINXOPTS    = "-W"
 SPHINXBUILD   = sphinx-build
 PAPER         =
 BUILDDIR      = build