diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
index ab5b2954f6b5..c6f499b82506 100644
--- a/nixos/modules/installer/tools/nixos-generate-config.pl
+++ b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -22,7 +22,7 @@ sub uniq {
 
 sub runCommand {
     my ($cmd) = @_;
-    open FILE, "$cmd 2>/dev/null |" or die "Failed to execute: $cmd\n";
+    open FILE, "$cmd 2>&1 |" or die "Failed to execute: $cmd\n";
     my @ret = <FILE>;
     close FILE;
     return ($?, @ret);
@@ -311,10 +311,13 @@ foreach my $fs (read_file("/proc/self/mountinfo")) {
 
     # Maybe this is a bind-mount of a filesystem we saw earlier?
     if (defined $fsByDev{$fields[2]}) {
-        my $path = $fields[3]; $path = "" if $path eq "/";
-        my $base = $fsByDev{$fields[2]};
-        $base = "" if $base eq "/";
-        $fileSystems .= <<EOF;
+        # Make sure this isn't a btrfs subvolume
+        my ($status, @msg) = runCommand("btrfs subvol show $rootDir$mountPoint");
+        if (join("", @msg) =~ /ERROR:/) {
+            my $path = $fields[3]; $path = "" if $path eq "/";
+            my $base = $fsByDev{$fields[2]};
+            $base = "" if $base eq "/";
+            $fileSystems .= <<EOF;
   fileSystems.\"$mountPoint\" =
     { device = \"$base$path\";
       fsType = \"none\";
@@ -322,7 +325,8 @@ foreach my $fs (read_file("/proc/self/mountinfo")) {
     };
 
 EOF
-        next;
+            next;
+        }
     }
     $fsByDev{$fields[2]} = $mountPoint;
 
@@ -347,7 +351,7 @@ EOF
     # Is this a btrfs filesystem?
     if ($fsType eq "btrfs") {
         my ($status, @id_info) = runCommand("btrfs subvol show $rootDir$mountPoint");
-        if ($status != 0) {
+        if ($status != 0 || join("", @msg) =~ /ERROR:/) {
             die "Failed to retreive subvolume info for $mountPoint\n";
         }
         my @ids = join("", @id_info) =~ m/Object ID:[ \t\n]*([^ \t\n]*)/;