diff --git a/doc/manual/conf-file.xml b/doc/manual/conf-file.xml
index c19e44ebf..c09d46206 100644
--- a/doc/manual/conf-file.xml
+++ b/doc/manual/conf-file.xml
@@ -329,6 +329,19 @@ build-use-chroot = /dev /proc /bin</programlisting>
   </varlistentry>
 
 
+  <varlistentry><term><literal>trusted-binary-caches</literal></term>
+
+    <listitem><para>A list of URLs of binary caches, separated by
+    whitespace.  These are not used by default, but can be enabled by
+    users of the Nix daemon by specifying <literal>--option
+    binary-caches <replaceable>urls</replaceable></literal> on the
+    command line.  Daemon users are only allowed to pass a subset of
+    the URLs listed in <literal>binary-caches</literal> and
+    <literal>trusted-binary-caches</literal>.</para></listitem>
+
+  </varlistentry>
+
+
   <varlistentry><term><literal>binary-caches-parallel-connections</literal></term>
 
     <listitem><para>The maximum number of parallel HTTP connections
diff --git a/scripts/download-from-binary-cache.pl.in b/scripts/download-from-binary-cache.pl.in
index 5d65e664e..3f7d3ef45 100644
--- a/scripts/download-from-binary-cache.pl.in
+++ b/scripts/download-from-binary-cache.pl.in
@@ -8,6 +8,7 @@ use Nix::Store;
 use Nix::Utils;
 use WWW::Curl::Easy;
 use WWW::Curl::Multi;
+use List::MoreUtils qw(any);
 use strict;
 
 
@@ -166,9 +167,32 @@ sub getAvailableCaches {
     return if $gotCaches;
     $gotCaches = 1;
 
-    my @urls = map { s/\/+$//; $_ } split(/ /,
-        $Nix::Config::config{"binary-caches"}
-        // ($Nix::Config::storeDir eq "/nix/store" ? "http://nixos.org/binary-cache" : ""));
+    sub strToList {
+        my ($s) = @_;
+        return map { s/\/+$//; $_ } split(/ /, $s);
+    }
+
+    my @urls = strToList
+        ($Nix::Config::config{"binary-caches"}
+         // ($Nix::Config::storeDir eq "/nix/store" ? "http://nixos.org/binary-cache" : ""));
+
+    # Allow Nix daemon users to override the binary caches to a subset
+    # of those listed in the config file.  Note that ‘untrusted-*’
+    # denotes options passed by the client.
+    if (defined $Nix::Config::config{"untrusted-binary-caches"}) {
+        my @untrustedUrls = strToList $Nix::Config::config{"untrusted-binary-caches"};
+        my @trustedUrls = (@urls, strToList($Nix::Config::config{"trusted-binary-caches"} // ""));
+        @urls = ();
+        foreach my $url (@untrustedUrls) {
+            if (any { $url eq $_ } @trustedUrls) {
+                push @urls, $url;
+            } else {
+                # FIXME: should die here, but we currently can't
+                # deliver error messages to clients.
+                warn "warning: binary cache ‘$url’ is not trusted (please add it to ‘trusted-binary-caches’ in $Nix::Config::confDir/nix.conf)\n";
+            }
+        }
+    }
 
     foreach my $url (@urls) {