diff --git a/default.nix b/default.nix
index a96232f..188f0fd 100644
--- a/default.nix
+++ b/default.nix
@@ -52,7 +52,7 @@
 }:
 let
   inherit (lib) optionalAttrs optionalString;
-  inherit (import ./fetch-overrides.nix) extraPins extraUrls;
+  inherit (import ./fetch-overrides.nix) extraPins extraUrls allRefsRepos;
 
   # Step 1: determine which Emacs packages to pull in.
   #
@@ -237,6 +237,7 @@ let
               {
                 inherit url;
                 rev = pin;
+                allRefs = allRefsRepos.${url} or false;
                 submodules = !(p.recipe.nonrecursive or false);
                 # TODO: pull ref from derivation.src when not pulling it from p.recipe?
                 # Note Doom does have packages with pin + branch (or nonrecursive) set,
diff --git a/fetch-overrides.nix b/fetch-overrides.nix
index 9151a4a..fda9422 100644
--- a/fetch-overrides.nix
+++ b/fetch-overrides.nix
@@ -34,4 +34,9 @@
     # Looks stable enough we can get away with pinning it.
     "sly-stepper" = "da84e3bba8466c2290c2dc7c27d7f4c48c27b39e";
   };
+
+  # TODO figure out whether we're better off always setting allRefs.
+  allRefsRepos = {
+    "https://git.savannah.gnu.org/git/emms.git" = true;
+  };
 }