diff --git a/transport/ServiceManagement.cpp b/transport/ServiceManagement.cpp
index 5795b02..cdcfd0e 100644
--- a/transport/ServiceManagement.cpp
+++ b/transport/ServiceManagement.cpp
@@ -198,7 +198,7 @@
                     vec.push_back({
                         .interfaceName = matchedName,
                         .instanceName = "",
-                        .refCount = 0,
+                        .refCount = -1,
                     });
                 }
             }
diff --git a/transport/manager/1.0/IServiceManager.hal b/transport/manager/1.0/IServiceManager.hal
index ff7201e..10823ca 100644
--- a/transport/manager/1.0/IServiceManager.hal
+++ b/transport/manager/1.0/IServiceManager.hal
@@ -111,7 +111,8 @@
     struct InstanceDebugInfo {
         string interfaceName;
         string instanceName;
-        uint64_t refCount;
+        // negative values means N/A.
+        int64_t refCount;
     };
 
     /*