diff --git a/docs/checks/alerts/count.md b/docs/checks/alerts/count.md
index 4ca9ea0e..7b8febad 100644
--- a/docs/checks/alerts/count.md
+++ b/docs/checks/alerts/count.md
@@ -9,7 +9,7 @@ grand_parent: Documentation
 This check is used to estimate how many times given alert would fire.
 It will run `expr` query from every alert rule against selected Prometheus
 servers and report how many unique alerts it would generate.
-If `for` is set on alerts it will be used to adjust results.
+If `for` and/or `keep_firing_for` are set on alerts they will be used to adjust results.
 
 ## Configuration
 
diff --git a/internal/checks/alerts_count.go b/internal/checks/alerts_count.go
index e96f3727..5d119516 100644
--- a/internal/checks/alerts_count.go
+++ b/internal/checks/alerts_count.go
@@ -89,10 +89,15 @@ func (c AlertsCheck) Check(ctx context.Context, _ string, rule parser.Rule, _ []
 	if rule.AlertingRule.For != nil {
 		forDur, _ = model.ParseDuration(rule.AlertingRule.For.Value.Value)
 	}
+	var keepFiringForDur model.Duration
+	if rule.AlertingRule.For != nil {
+		keepFiringForDur, _ = model.ParseDuration(rule.AlertingRule.KeepFiringFor.Value.Value)
+	}
 
 	var alerts int
 	for _, r := range qr.Series.Ranges {
-		if r.End.Sub(r.Start) > time.Duration(forDur) {
+		// If `keepFiringFor` is not defined its Duration will be 0
+		if r.End.Sub(r.Start) > (time.Duration(forDur) + time.Duration(keepFiringForDur)) {
 			alerts++
 		}
 	}