diff --git a/bin/compile b/bin/compile
index a8bd024..858e706 100755
--- a/bin/compile
+++ b/bin/compile
@@ -48,7 +48,7 @@ export PATH=$PATH:$ROOT_DIR/vendor/:$ROOT_DIR/vendor/pip-pop
 
 # Sanitizing environment variables.
 unset GIT_DIR PYTHONHOME PYTHONPATH
-unset RECEIVE_DATA RUN_KEY BUILD_INFO DEPLOY LOG_TOKEN DYNO
+unset RECEIVE_DATA RUN_KEY BUILD_INFO DEPLOY LOG_TOKEN
 unset CYTOKINE_LOG_FILE GEM_PATH
 
 # Syntax sugar.
diff --git a/bin/utils b/bin/utils
index c8785d0..8d037fe 100755
--- a/bin/utils
+++ b/bin/utils
@@ -88,7 +88,7 @@ deep-rm() {
 sub-env() {
 
   WHITELIST=${2:-''}
-  BLACKLIST=${3:-'^(GIT_DIR|PYTHONHOME|LD_LIBRARY_PATH|LIBRARY_PATH|PATH)$'}
+  BLACKLIST=${3:-'^(GIT_DIR|STACK|PYTHONHOME|LD_LIBRARY_PATH|LIBRARY_PATH|PATH)$'}
 
   # Python-specific variables.
   export PYHONHOME=$BUILD_DIR/.heroku/python