diff --git a/src/build.py b/src/build.py
index 07e5d42592..7e322aaa31 100755
--- a/src/build.py
+++ b/src/build.py
@@ -483,6 +483,9 @@ def make_package(args):
     if args.resource is None:
         args.resource = []
 
+    if args.manifest_extra is None:
+        args.manifest_extra = []
+
     if args.compile_pyo:
         if PYTHON is None:
             ap.error('To use --compile-pyo, you need Python 2.7.1 installed '