diff --git a/Makefile.am b/Makefile.am
index 651d462e483f91d931148472cb9ec43dc2f99f88..f799d617ebce96b2d0c96723cc39f220484b5568 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -152,7 +152,7 @@ doc/html: $(docrst) $(docpng) doc/conf.py configure.ac
 	@test -n "$(SPHINX)" || \
 	    { echo 'sphinx-build' not found during configure; exit 1; }
 	mkdir -p doc/build/doctrees
-	PYTHONPATH=.:$(top_builddir) sphinx-build -q -b html \
+	PYTHONPATH=.:$(top_builddir) $(SPHINX) -q -b html \
 	    -d doc/build/doctrees \
 	    -D version="$(VERSION_MAJOR).$(VERSION_MINOR)" \
 	    -D release="$(PACKAGE_VERSION)" \