diff --git a/src/PIL/_version.py b/src/PIL/_version.py
index 56dac78bb..2835370a2 100644
--- a/src/PIL/_version.py
+++ b/src/PIL/_version.py
@@ -1,2 +1,2 @@
 # Master version for Pillow
-__version__ = '5.4.0'
+__version__ = '5.5.0.dev0'