diff --git a/event_extra.go b/event_extra.go
index 6e29d40..693e099 100644
--- a/event_extra.go
+++ b/event_extra.go
@@ -2,6 +2,9 @@ package nostr
 
 // SetExtra sets an out-of-the-spec value under the given key into the event object.
 func (evt *Event) SetExtra(key string, value any) {
+	if evt.extra == nil {
+		evt.extra = make(map[string]any)
+	}
 	evt.extra[key] = value
 }