diff --git a/builds/cedar-14.Dockerfile~move Dockerfiles to central location, add all stacks, update README b/builds/cedar-14.Dockerfile~move Dockerfiles to central location, add all stacks, update README
index 921b437..f82fa16 100644
--- a/builds/cedar-14.Dockerfile~move Dockerfiles to central location, add all stacks, update README	
+++ b/builds/cedar-14.Dockerfile~move Dockerfiles to central location, add all stacks, update README	
@@ -3,7 +3,8 @@ FROM heroku/cedar:14
 WORKDIR /app
 ENV WORKSPACE_DIR="/app/builds" \
     S3_BUCKET="lang-python" \
-    S3_PREFIX="cedar-14/"
+    S3_PREFIX="cedar-14/" \
+    STACK="cedar-14"
 
 RUN apt-get update && apt-get install -y python-pip && rm -rf /var/lib/apt/lists/*
 
diff --git a/builds/heroku-18.Dockerfile~move Dockerfiles to central location, add all stacks, update README b/builds/heroku-18.Dockerfile~move Dockerfiles to central location, add all stacks, update README
index 466506a..6288ac0 100644
--- a/builds/heroku-18.Dockerfile~move Dockerfiles to central location, add all stacks, update README	
+++ b/builds/heroku-18.Dockerfile~move Dockerfiles to central location, add all stacks, update README	
@@ -4,7 +4,8 @@ WORKDIR /app
 ENV WORKSPACE_DIR="/app/builds" \
     S3_BUCKET="lang-python" \
     S3_PREFIX="heroku-18/" \
-    DEBIAN_FRONTEND=noninteractive
+    DEBIAN_FRONTEND=noninteractive \
+    STACK="heroku-18"
 
 RUN apt-get update && apt-get install -y python-pip && rm -rf /var/lib/apt/lists/*