diff --git a/doc/Makefile b/doc/Makefile
index d4bb2cb..d0ac5f2 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -4,7 +4,7 @@
 # You can set these variables from the command line, and also
 # from the environment for the first two.
 SPHINXOPTS    ?=
-SPHINXBUILD   ?= sphinx-build
+SPHINXBUILD   ?= python $(shell which sphinx-build)
 SOURCEDIR     = .
 BUILDDIR      = _build