diff --git a/src/zm_zone.h b/src/zm_zone.h
index bfd39e9aa..9ac8371f0 100644
--- a/src/zm_zone.h
+++ b/src/zm_zone.h
@@ -77,6 +77,7 @@ protected:
 
   // Outputs/Statistics
   bool      alarmed;
+  bool      was_alarmed;
   int        pixel_diff;
   unsigned int      alarm_pixels;
   int        alarm_filter_pixels;