diff --git a/doc/Makefile b/doc/Makefile
index cae96bdb67392c43ff359b262b3c218ece5947ef..cd9f910938e3358daaf585921710b3b3c4081df8 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -3,7 +3,7 @@
 
 # You can set these variables from the command line.
 SPHINXOPTS    =
-SPHINXBUILD   = sphinx-build
+SPHINXBUILD   = python `which sphinx-build`
 PAPER         =
 BUILDDIR      = _build