diff --git a/.platform.app.yaml b/.platform.app.yaml
index 946c6f7c152..53c3a99f7b3 100644
--- a/.platform.app.yaml
+++ b/.platform.app.yaml
@@ -52,4 +52,4 @@ dependencies:
 hooks:
     build: |
       pip install git+https://github.com/fabpot/sphinx-php.git
-      make html
+      make -C _build html
diff --git a/_build/Makefile b/_build/Makefile
index a37807af545..25b660056fe 100644
--- a/_build/Makefile
+++ b/_build/Makefile
@@ -5,12 +5,12 @@
 SPHINXOPTS    =
 SPHINXBUILD   = sphinx-build
 PAPER         =
-BUILDDIR      = _build
+BUILDDIR      = .
 
 # Internal variables.
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter
-ALLSPHINXOPTS   = -d $(BUILDDIR)/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
+ALLSPHINXOPTS   = -c $(BUILDDIR) -d $(BUILDDIR)/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) ../
 # the i18n builder cannot share the environment and doctrees with the others
 I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .