diff --git a/python-OWSLib.spec b/python-OWSLib.spec
index 14cd2bc..9069317 100644
--- a/python-OWSLib.spec
+++ b/python-OWSLib.spec
@@ -93,7 +93,8 @@ echo 'nbsphinx_allow_errors = True' >> docs/conf.py
 %pyproject_wheel
 
 %if %{with doc_pdf}
-PYTHONPATH="${PWD}" %make_build -C docs latex SPHINXOPTS='%{?_smp_mflags}'
+PYTHONPATH="${PWD}" %make_build -C docs latex \
+    SPHINXOPTS='-j%{?_smp_build_ncpus}'
 %make_build -C docs/build/latex/en LATEXMKOPTS='-quiet'
 %endif