diff --git a/requirements.txt b/requirements.txt
index 717fe4d..77e7f1d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,6 @@
+Pillow>=4.3.0
+
+# -- dev --
 pytest>=3.3.1
 coveralls>=1.2.0
 coverage>=4.4.2