diff --git a/docs/Makefile b/docs/Makefile
index c5143bd..049f749 100644
--- a/docs/Makefile
+++ b/docs/Makefile
@@ -12,7 +12,7 @@ PYTHON        = python3
 # Internal variables.
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter
-ALLSPHINXOPTS   = -d build/doctrees -W $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) $(SRCDIR)
+ALLSPHINXOPTS   = -d build/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) $(SRCDIR)
 
 .PHONY: help clean html web pickle htmlhelp latex changes linkcheck api