diff --git a/grumpy-runtime-src/MANIFEST.in b/grumpy-runtime-src/MANIFEST.in
index 16d47166..9e95f127 100644
--- a/grumpy-runtime-src/MANIFEST.in
+++ b/grumpy-runtime-src/MANIFEST.in
@@ -8,3 +8,5 @@ global-exclude *.egg-info/*
 global-exclude *__pycache__*
 
 recursive-exclude grumpy-tools-src *.go
+
+include pyproject.toml
diff --git a/grumpy-runtime-src/Makefile b/grumpy-runtime-src/Makefile
index 65ae68aa..8b60fe95 100644
--- a/grumpy-runtime-src/Makefile
+++ b/grumpy-runtime-src/Makefile
@@ -50,8 +50,12 @@ PY_DIR := build/lib/python2.7/site-packages
 PY_INSTALL_DIR := $(shell $(PYTHON) -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())")
 
 export GOPATH := $(ROOT_DIR)/build
-export PYTHONPATH := $(ROOT_DIR)/$(PY_DIR)
 export PATH := $(ROOT_DIR)/build/bin:$(PATH)
+ifndef PYTHONPATH
+  export PYTHONPATH := $(ROOT_DIR)/$(PY_DIR)
+else
+  export PYTHONPATH := $(PYTHONPATH):$(ROOT_DIR)/$(PY_DIR)
+endif
 
 GOPATH_PY_ROOT := $(GOPATH)/src/__python__
 
diff --git a/grumpy-runtime-src/pyproject.toml b/grumpy-runtime-src/pyproject.toml
new file mode 100644
index 00000000..3d6d2d23
--- /dev/null
+++ b/grumpy-runtime-src/pyproject.toml
@@ -0,0 +1,2 @@
+[build-system]
+requires = ["setuptools", "wheel", "grumpy-tools>0.2.2"]