diff --git a/CHANGELOG.md b/CHANGELOG.md
index 780a159..a9157fc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
     - Pre-flight errors are now displayed also after the usage text to prevent the need to scroll through backlog.
     - Cancelling via SIGINT (Ctrl-C) is now more responsive
     - Fixed issue where a thread would hang due to TCP errors
+    - Fixed the issue where the option -ac was overwriting existing filters. Now auto-calibration will add them where needed.
     - The `-w` flag now accepts comma delimited values in the form of `file1:W1,file2:W2`.
 
 - v1.1.0
diff --git a/pkg/filter/filter.go b/pkg/filter/filter.go
index e4570aa..8f266b4 100644
--- a/pkg/filter/filter.go
+++ b/pkg/filter/filter.go
@@ -30,11 +30,21 @@ func NewFilterByName(name string, value string) (ffuf.FilterProvider, error) {
 
 //AddFilter adds a new filter to Config
 func AddFilter(conf *ffuf.Config, name string, option string) error {
-	newf, err := NewFilterByName(name, option)
-	if err == nil {
-		conf.Filters[name] = newf
-	}
-	return err
+        newf, err := NewFilterByName(name, option)
+        if err == nil {
+                // valid filter create or append
+                if conf.Filters[name] == nil {
+                        conf.Filters[name] = newf
+                } else {
+                        currentfilter := conf.Filters[name].Repr()
+                        newoption := strings.TrimSpace(strings.Split(currentfilter, ":")[1]) + "," + option
+                        newerf, err := NewFilterByName(name, newoption)
+                        if err == nil {
+                                conf.Filters[name] = newerf
+                        }
+                }
+        }
+        return err
 }
 
 //AddMatcher adds a new matcher to Config