diff --git a/src/zm_monitor.cpp b/src/zm_monitor.cpp
index 8a1aabe63..8c097fb29 100644
--- a/src/zm_monitor.cpp
+++ b/src/zm_monitor.cpp
@@ -1052,6 +1052,7 @@ bool Monitor::disconnect() {
     return true;
   }
 
+  shared_data->valid = false;
 #if ZM_MEM_MAPPED
   msync(mem_ptr, mem_size, MS_ASYNC);
   munmap(mem_ptr, mem_size);