diff --git a/mace/core/net.cc b/mace/core/net.cc
index 2933df8c4aec358afc5f15637747ecb92ae4a1ca..22956876262c5b16a042e9e1289e6fd4fc73dca6 100644
--- a/mace/core/net.cc
+++ b/mace/core/net.cc
@@ -55,4 +55,4 @@ unique_ptr<NetBase> CreateNet(
 }
 
 
-} //  namespace mace
\ No newline at end of file
+} //  namespace mace
diff --git a/mace/core/registry.h b/mace/core/registry.h
index f098933582d3a09f322a822c43f0ea0b195c4053..e37a51cab92763ad3f339e3512710e7e9bae9bf7 100644
--- a/mace/core/registry.h
+++ b/mace/core/registry.h
@@ -26,6 +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;
     }
     return registry_[key](args...);
diff --git a/mace/examples/README.md b/mace/examples/README.md
index 4feb5c8d88ba45f7ff84b5e28a145843a3d0a1c3..b9be3027d05100cf7c8ce41932292d0ec8d6107b 100644
--- a/mace/examples/README.md
+++ b/mace/examples/README.md
@@ -3,7 +3,11 @@ Examples
 
 * Build the example (e.g., with armeabi-v7a target)
 ```
-bazel build mace/examples:helloworld \
+# To enable debug mode build, use '-c dbg' flag.
+# To check the underlying commands executed, use '-s' flag.
+# TO check the failed command, use '--verbose_failures' flag.
+
+bazel build -c opt mace/examples:helloworld \
    --crosstool_top=//external:android/crosstool \
    --host_crosstool_top=@bazel_tools//tools/cpp:toolchain \
    --cpu=armeabi-v7a
diff --git a/mace/ops/relu.cc b/mace/ops/relu.cc
index a31c25ddf96b8fbc5ffd1233690576f3b4d5a57d..94646e0f3eca5c21bd8eb4510f2c5a41c54f7a05 100644
--- a/mace/ops/relu.cc
+++ b/mace/ops/relu.cc
@@ -25,4 +25,4 @@ bool ReluOp<DeviceType::CPU, float>::Run() {
 
 REGISTER_CPU_OPERATOR(Relu, ReluOp<DeviceType::CPU, float>);
 
-} //  namespace mace
\ No newline at end of file
+} //  namespace mace