diff --git a/lib/types/populate.nix b/lib/types/populate.nix
index 49996f6..bf90ace 100644
--- a/lib/types/populate.nix
+++ b/lib/types/populate.nix
@@ -81,6 +81,10 @@
             type = lib.types.listOf lib.types.str;
           };
         };
+        fetchAlways = lib.mkOption {
+          type = lib.types.bool;
+          default = false;
+        };
         ref = lib.mkOption {
           type = lib.types.str; # TODO lib.types.git.ref
         };
diff --git a/pkgs/populate/default.nix b/pkgs/populate/default.nix
index ad70d2e..1367a50 100644
--- a/pkgs/populate/default.nix
+++ b/pkgs/populate/default.nix
@@ -66,9 +66,13 @@ let
     hash=${quote source.ref}
 
     if ! test "$(git log --format=%H -1)" = "$hash"; then
-      if ! git log -1 "$hash" >/dev/null 2>&1; then
+      ${if source.fetchAlways then /* sh */ ''
         git fetch origin
-      fi
+      '' else /* sh */ ''
+        if ! git log -1 "$hash" >/dev/null 2>&1; then
+          git fetch origin
+        fi
+      ''}
       git reset --hard "$hash" >&2
       git submodule update --init --recursive
     fi