diff --git a/dnsfilter/dnsfilter.go b/dnsfilter/dnsfilter.go
index 2902c75a..eed6bd33 100644
--- a/dnsfilter/dnsfilter.go
+++ b/dnsfilter/dnsfilter.go
@@ -13,6 +13,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"runtime"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -772,18 +773,31 @@ func (d *Dnsfilter) initFiltering(filters map[int]string) error {
 			list = &urlfilter.StringRuleList{
 				ID:             0,
 				RulesText:      dataOrFilePath,
-				IgnoreCosmetic: false,
+				IgnoreCosmetic: true,
 			}
 
 		} else if !fileExists(dataOrFilePath) {
 			list = &urlfilter.StringRuleList{
 				ID:             id,
-				IgnoreCosmetic: false,
+				IgnoreCosmetic: true,
+			}
+
+		} else if runtime.GOOS == "windows" {
+			// On Windows we don't pass a file to urlfilter because
+			//  it's difficult to update this file while it's being used.
+			data, err := ioutil.ReadFile(dataOrFilePath)
+			if err != nil {
+				return fmt.Errorf("ioutil.ReadFile(): %s: %s", dataOrFilePath, err)
+			}
+			list = &urlfilter.StringRuleList{
+				ID:             id,
+				RulesText:      string(data),
+				IgnoreCosmetic: true,
 			}
 
 		} else {
 			var err error
-			list, err = urlfilter.NewFileRuleList(id, dataOrFilePath, false)
+			list, err = urlfilter.NewFileRuleList(id, dataOrFilePath, true)
 			if err != nil {
 				return fmt.Errorf("urlfilter.NewFileRuleList(): %s: %s", dataOrFilePath, err)
 			}
diff --git a/home/filter.go b/home/filter.go
index 415ba783..72835a92 100644
--- a/home/filter.go
+++ b/home/filter.go
@@ -217,8 +217,12 @@ func refreshFilters() (int, error) {
 // . For each filter run the download and checksum check operation
 // . For each filter:
 //  . If filter data hasn't changed, just set new update time on file
-//  . If filter data has changed: rename the old file, store the new data on disk
-//  . Pass new filters to dnsfilter object
+//  . If filter data has changed:
+//    . rename the old file (1.txt -> 1.txt.old)
+//    . store the new data on disk (1.txt)
+//  . Pass new filters to dnsfilter object - it analyzes new data while the old filters are still active
+//  . dnsfilter activates new filters
+//  . Remove the old filter files (1.txt.old)
 func refreshFiltersIfNecessary(force bool) int {
 	var updateFilters []filter
 	var updateFlags []bool // 'true' if filter data has changed
@@ -431,7 +435,10 @@ func (filter *filter) save() error {
 
 func (filter *filter) saveAndBackupOld() error {
 	filterFilePath := filter.Path()
-	_ = os.Rename(filterFilePath, filterFilePath+".old")
+	err := os.Rename(filterFilePath, filterFilePath+".old")
+	if err != nil {
+		return err
+	}
 	return filter.save()
 }