diff --git a/config-daemon.ac b/config-daemon.ac
index 825b5971df..6cf65bef1d 100644
--- a/config-daemon.ac
+++ b/config-daemon.ac
@@ -120,7 +120,15 @@ if test "x$guix_build_daemon" = "xyes"; then
 
   dnl Determine the appropriate default list of substitute URLs (GnuTLS
   dnl is required so we can default to 'https'.)
-  guix_substitute_urls="https://mirror.hydra.gnu.org"
+  case "x$host_cpu" in
+    xaarch64)
+      # Currently only berlin.guixsd.org provides aarch64 binaries.
+      guix_substitute_urls="https://berlin.guixsd.org"
+      ;;
+    *)
+      guix_substitute_urls="https://mirror.hydra.gnu.org"
+      ;;
+  esac
 
   AC_MSG_CHECKING([for default substitute URLs])
   AC_MSG_RESULT([$guix_substitute_urls])