diff --git a/utils/mask/requirements.txt b/utils/mask/requirements.txt
index b34ef047..e05795da 100644
--- a/utils/mask/requirements.txt
+++ b/utils/mask/requirements.txt
@@ -2,7 +2,7 @@ wheel
 setuptools
 cython>=0.28.3
 argparse>=1.1
-numpy=1.16.4
+numpy==1.16.4
 lxml>=3.5.0
 glog>=0.3.1
 tqdm>=4.19.6