diff --git a/src/action.h b/src/action.h
index 3fca164febc98992c21eabf7f563441b0c8e7f81..3d7a0bdec96f14fabbe5d2c8fd2f45cae3221d84 100644
--- a/src/action.h
+++ b/src/action.h
@@ -49,6 +49,7 @@ enum class Action {
     stopAdc,
     fillHistogram,
     clearHistogram,
+    error,
 };
 }