diff --git a/lib/py/Makefile.am b/lib/py/Makefile.am
index 24c5892..7db5c3b 100644
--- a/lib/py/Makefile.am
+++ b/lib/py/Makefile.am
@@ -5,4 +5,4 @@
 # Old version (can't put inline because it's not portable).
 #$(PYTHON) setup.py install --prefix=$(prefix) --root=$(DESTDIR) $(PYTHON_SETUPUTIL_ARGS)
 install-exec-hook:
-	$(PYTHON) setup.py install --root=$(DESTDIR) $(PYTHON_SETUPUTIL_ARGS)
+	$(PYTHON) setup.py install --root=$(DESTDIR) --prefix=$(PY_PREFIX) $(PYTHON_SETUPUTIL_ARGS)