diff --git a/heka/files/lua/common/gse.lua b/heka/files/lua/common/gse.lua
index d1a01a6..3e6948e 100644
--- a/heka/files/lua/common/gse.lua
+++ b/heka/files/lua/common/gse.lua
@@ -95,8 +95,16 @@
 function set_member_status(cluster_id, member, value, alarms, hostname)
     local cluster = clusters[cluster_id]
     if cluster then
+        if cluster.group_by == 'hostname' and not hostname then
+            local err = string.format(
+                'Cannot update member status of cluster %s; ' ..
+                'group_by is set to "hostname" while input GSE/AFD message ' ..
+                'has no "hostname" field', cluster_id)
+            return false, err
+        end
         cluster:update_fact(member, hostname, value, alarms)
     end
+    return true
 end
 
 -- The cluster status depends on the status of its members.
diff --git a/heka/files/lua/filters/gse_cluster_filter.lua b/heka/files/lua/filters/gse_cluster_filter.lua
index d1fef2b..2bf6926 100644
--- a/heka/files/lua/filters/gse_cluster_filter.lua
+++ b/heka/files/lua/filters/gse_cluster_filter.lua
@@ -72,8 +72,13 @@
 
     -- update all clusters that depend on this entity
     for _, cluster_id in ipairs(cluster_ids) do
-        gse.set_member_status(cluster_id, member_id, status, alarms, hostname)
+        local ok, err = gse.set_member_status(
+            cluster_id, member_id, status, alarms, hostname)
+        if not ok then
+            return -1, err
+        end
     end
+
     return 0
 end