diff --git a/mace/core/net.cc b/mace/core/net.cc
index e6c20cda1217f060985e59b3f3eb7f02559d5774..d914226e8b906db39c1437b9f2c751eccfc0f460 100644
--- a/mace/core/net.cc
+++ b/mace/core/net.cc
@@ -23,7 +23,9 @@ SimpleNet::SimpleNet(const std::shared_ptr<const NetDef>& net_def,
     std::unique_ptr<OperatorBase> op{nullptr};
     OperatorDef temp_def(operator_def);
     op = CreateOperator(temp_def, ws, type);
-    operators_.emplace_back(std::move(op));
+    if (!op) {
+      operators_.emplace_back(std::move(op));
+    }
   }
 }
 bool SimpleNet::Run() {
diff --git a/mace/core/registry.h b/mace/core/registry.h
index 08ea209d0160f96c34e558fa5a205c32555a17e3..1295128cf1446fc53a996ed1a0910eea3ccb3df1 100644
--- a/mace/core/registry.h
+++ b/mace/core/registry.h
@@ -26,8 +26,7 @@ class Registry {
 
   unique_ptr<ObjectType> Create(const SrcType& key, Args... args) {
     if (registry_.count(key) == 0) {
-      VLOG(2) << "Key not registered: " << key;
-      return nullptr;
+      LOG(FATAL) << "Key not registered: " << key;
     }
     return registry_[key](args...);
   }