diff --git a/prometheus/main.go b/prometheus/main.go
index 707ae79..77ce15b 100644
--- a/prometheus/main.go
+++ b/prometheus/main.go
@@ -2,6 +2,7 @@ package prometheus
 
 import (
 	"fmt"
+	"strings"
 
 	"net/http"
 
@@ -30,8 +31,8 @@ func init() {
 			}
 
             contentTag := request.Status
-            if len(request.Alerts.Firing) > 0 {
-                contentTag += ":" + len(request.Alerts.Firing)
+            if len(request.Alerts.Firing()) > 0 {
+                contentTag += ":" + len(request.Alerts.Firing())
             }
             
             content := fmt.Sprintf("[%s] %s", contentTag, strings.Join(request.CommonAnnotations.Values()," "))