diff --git a/scripts/runner.pl b/scripts/runner.pl
index eefe3fd..dd225c9 100644
--- a/scripts/runner.pl
+++ b/scripts/runner.pl
@@ -44,14 +44,19 @@ sub update_db_config {
     open( my $readhandle, '<', $remote_db_conf )
       or die "failed to open db.conf: $!";
     my @lines;
+    my $found = 0;
     while ( my $line = <$readhandle> ) {
         if ( $line =~ /^database=/ ) {
-            $line = "database=$db_prefix\_$experiment";
+            $line  = "database=${db_prefix}_$experiment\n";
+            $found = 1;
         }
         push @lines, $line;
     }
     close($readhandle) or die "failed to close db.conf: $!";
 
+    die "no database= line found in $remote_db_conf for some reason"
+      unless $found;
+
     open( my $writehandle, '>', $remote_db_conf )
       or die "failed to open db.conf: $!";
     print( $writehandle, @lines );