diff --git a/files/etc/apt/sources.list.d/src-sid.list b/files/etc/apt/sources.list.d/src-sid.list
new file mode 100644
index 0000000000000000000000000000000000000000..6ef3a692ffa9e647610a608f8fe00625fff0f840
--- /dev/null
+++ b/files/etc/apt/sources.list.d/src-sid.list
@@ -0,0 +1,7 @@
+# Configure the build servers to get source packages from unstable by
+# default.  This is more useful when backporting.
+
+deb-src http://debian.stanford.edu/debian          sid main non-free contrib
+deb-src http://debian.stanford.edu/debian-stanford sid main non-free contrib
+deb-src http://debian.stanford.edu/debian-local    sid main non-free contrib
+