diff --git a/stackrc b/stackrc
index 3a19cdb..badde68 100644
--- a/stackrc
+++ b/stackrc
@@ -120,3 +120,6 @@
 if [ -f $RC_DIR/localrc ]; then
     source $RC_DIR/localrc
 fi
+
+# 5Gb default volume backing file size
+VOLUME_BACKING_FILE_SIZE=${VOLUME_BACKING_FILE_SIZE:-5130M}