diff --git a/docs/Makefile b/docs/Makefile
index 9f2209a8d62511f16eb59433b32092f16d3899a5..83ad6b7c03a0bdf7647f8f8496d126610465f8fb 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -13,7 +13,7 @@
 #
 
 # You can set these variables from the command line.
-SPHINXOPTS    =
+SPHINXOPTS    = -W
 SPHINXBUILD   = sphinx-build
 SPHINXPROJ    = Gimmecert
 SOURCEDIR     = .