diff --git a/apm-protocol/apm-ui-protocol/src/main/resources/ui-graphql/common.graphqls b/apm-protocol/apm-ui-protocol/src/main/resources/ui-graphql/common.graphqls
index 853f36258..ef552f7e8 100644
--- a/apm-protocol/apm-ui-protocol/src/main/resources/ui-graphql/common.graphqls
+++ b/apm-protocol/apm-ui-protocol/src/main/resources/ui-graphql/common.graphqls
@@ -56,8 +56,8 @@ type SLATrend {
 
 # The overview topology of the whole application cluster or services,
 type Topology {
-    nodes: [Node]!
-    calls: [Call]
+    nodes: [Node!]
+    calls: [Call!]
 }
 
 # The base Node of all node types in topology