diff --git a/scripts/demo.sh b/scripts/demo.sh
index 3aa2a10..9d2a415 100755
--- a/scripts/demo.sh
+++ b/scripts/demo.sh
@@ -1,7 +1,7 @@
 export MXNET_CUDNN_AUTOTUNE_DEFAULT=0
 export PYTHONUNBUFFERED=1
 export MXNET_ENABLE_GPU_P2P=0
-export PYTHONPATH=incubator-mxnet/python/
+export PYTHONPATH=${PYTHONPATH}:incubator-mxnet/python/
 
 MODEL_PATH=model/
 RESULT_PATH=data/cityscape/results/
diff --git a/scripts/demo_single_image.sh b/scripts/demo_single_image.sh
index f12e375..d9dfad0 100755
--- a/scripts/demo_single_image.sh
+++ b/scripts/demo_single_image.sh
@@ -1,7 +1,7 @@
 export MXNET_CUDNN_AUTOTUNE_DEFAULT=0
 export PYTHONUNBUFFERED=1
 export MXNET_ENABLE_GPU_P2P=0
-export PYTHONPATH=incubator-mxnet/python/
+export PYTHONPATH=${PYTHONPATH}:incubator-mxnet/python/
 
 MODEL_PATH=model/
 PREFIX=${MODEL_PATH}final
diff --git a/scripts/eval.sh b/scripts/eval.sh
index 6e154d9..03eaa01 100644
--- a/scripts/eval.sh
+++ b/scripts/eval.sh
@@ -1,7 +1,7 @@
 export MXNET_CUDNN_AUTOTUNE_DEFAULT=0
 export PYTHONUNBUFFERED=1
 export MXNET_ENABLE_GPU_P2P=0
-export PYTHONPATH=incubator-mxnet/python/
+export PYTHONPATH=${PYTHONPATH}:incubator-mxnet/python/
 
 TRAIN_DIR=model/res50-fpn/cityscape/alternate/
 DATASET=Cityscape
diff --git a/scripts/train_alternate.sh b/scripts/train_alternate.sh
index 5dc883a..541a9ad 100755
--- a/scripts/train_alternate.sh
+++ b/scripts/train_alternate.sh
@@ -1,7 +1,7 @@
 export MXNET_CUDNN_AUTOTUNE_DEFAULT=0
 export PYTHONUNBUFFERED=1
 export MXNET_ENABLE_GPU_P2P=0
-export PYTHONPATH=incubator-mxnet/python/
+export PYTHONPATH=${PYTHONPATH}:incubator-mxnet/python/
 
 TRAIN_DIR=model/res50-fpn/cityscape/alternate/
 DATASET=Cityscape