diff --git a/modules/installer/tools/nixos-install.sh b/modules/installer/tools/nixos-install.sh
index aca2cca6a713..51270650429d 100644
--- a/modules/installer/tools/nixos-install.sh
+++ b/modules/installer/tools/nixos-install.sh
@@ -119,7 +119,7 @@ if test -n "$build_users_group"; then
 fi
 binary_caches=$(@perl@/bin/perl -e 'use Nix::Config; Nix::Config::readConfig; print $Nix::Config::config{"binary-caches"};')
 if test -n "$binary_caches"; then
-    echo "binary-caches $binary_caches" >> $mountPoint/tmp/nix.conf
+    echo "binary-caches = $binary_caches" >> $mountPoint/tmp/nix.conf
 fi
 export NIX_CONF_DIR=/tmp