diff --git a/src/detect-engine-alert.c b/src/detect-engine-alert.c
index d0a1329dbc..4844dc7aa9 100644
--- a/src/detect-engine-alert.c
+++ b/src/detect-engine-alert.c
@@ -198,6 +198,7 @@ int PacketAlertAppendTag(Packet *p, PacketAlert *pa)
     pa->class = 0;
     pa->class_msg = NULL;
     pa->references = NULL;
+    pa->alert_msg = NULL;
 
     return 0;
 }