diff --git a/modules/installer/tools/nixos-install.sh b/modules/installer/tools/nixos-install.sh
index 1b0bfc97f08..258f125db5d 100644
--- a/modules/installer/tools/nixos-install.sh
+++ b/modules/installer/tools/nixos-install.sh
@@ -38,7 +38,9 @@ fi
 
 # Do a nix-pull to speed up building.
 if test -n "@nixosURL@" -a ${NIXOS_PULL:-1} != 0; then
-    @nix@/bin/nix-pull @nixosURL@/MANIFEST || true
+    mkdir -p /nix/var/nix/channel-cache -m 0755
+    NIX_DOWNLOAD_CACHE=/nix/var/nix/channel-cache \
+        @nix@/bin/nix-pull @nixosURL@/MANIFEST || true
 fi