diff --git a/misc/build_helpers/Dockerfile b/misc/build_helpers/Dockerfile
index 6b45619bb..155ed846f 100644
--- a/misc/build_helpers/Dockerfile
+++ b/misc/build_helpers/Dockerfile
@@ -1,6 +1,6 @@
 FROM python:2.7
 
-ADD . /tahoe-lafs
+ADD ../.. /tahoe-lafs
 RUN \
   cd /tahoe-lafs && \
   make && \