diff --git a/lib/etcdv3/lock.rb b/lib/etcdv3/lock.rb
index a439d61..ce9b36c 100644
--- a/lib/etcdv3/lock.rb
+++ b/lib/etcdv3/lock.rb
@@ -10,12 +10,12 @@ def initialize(hostname, credentials, timeout, metadata = {})
 
     def lock(name, lease_id, timeout: nil)
       request = V3lockpb::LockRequest.new(name: name, lease: lease_id)
-      @stub.lock(request, deadline: deadline(timeout))
+      @stub.lock(request, metadata: @metadata, deadline: deadline(timeout))
     end
 
     def unlock(key, timeout: nil)
       request = V3lockpb::UnlockRequest.new(key: key)
-      @stub.unlock(request, deadline: deadline(timeout))
+      @stub.unlock(request, metadata: @metadata, deadline: deadline(timeout))
     end
 
     private
diff --git a/lib/etcdv3/namespace/lock.rb b/lib/etcdv3/namespace/lock.rb
index d31cd2a..76b60f6 100644
--- a/lib/etcdv3/namespace/lock.rb
+++ b/lib/etcdv3/namespace/lock.rb
@@ -13,14 +13,14 @@ def initialize(hostname, credentials, timeout, namespace, metadata = {})
     def lock(name, lease_id, timeout: nil)
       name = prepend_prefix(@namespace, name)
       request = V3lockpb::LockRequest.new(name: name, lease: lease_id)
-      resp = @stub.lock(request, deadline: deadline(timeout))
+      resp = @stub.lock(request, metadata: @metadata, deadline: deadline(timeout))
       strip_prefix_from_lock(@namespace, resp)
     end
 
     def unlock(key, timeout: nil)
       key = prepend_prefix(@namespace, key)
       request = V3lockpb::UnlockRequest.new(key: key)
-      @stub.unlock(request, deadline: deadline(timeout))
+      @stub.unlock(request, metadata: @metadata, deadline: deadline(timeout))
     end
 
     private
diff --git a/spec/etcdv3/lock_spec.rb b/spec/etcdv3/lock_spec.rb
index 39ac574..7917545 100644
--- a/spec/etcdv3/lock_spec.rb
+++ b/spec/etcdv3/lock_spec.rb
@@ -10,14 +10,28 @@
     #it_should_behave_like "a method with a GRPC timeout", described_class, :lock, :lock, 'foo'
 
     describe '#lock' do
-      let(:lease_id) { lease_stub.lease_grant(10)['ID'] }
-      subject { stub.lock('foo', lease_id) }
-      it { is_expected.to be_an_instance_of(V3lockpb::LockResponse) }
+      it 'returns a response' do
+        lease_id = lease_stub.lease_grant(10)['ID']
+
+        expect(stub.lock('example1', lease_id)).to be_an_instance_of(V3lockpb::LockResponse)
+      end
+
+      it 'passes metadata correctly' do
+        lease_id = lease_stub.lease_grant(10)['ID']
+        stub = expect_metadata_passthrough(described_class, :lock, :lock)
+        stub.lock('example2', lease_id)
+      end
     end
 
     describe '#unlock' do
-      subject { stub.unlock('foo') }
-      it { is_expected.to be_an_instance_of(V3lockpb::UnlockResponse) }
+      it 'returns a response' do
+        expect(stub.unlock('example3')).to be_an_instance_of(V3lockpb::UnlockResponse)
+      end
+
+      it 'passes metadata correctly' do
+        stub = expect_metadata_passthrough(described_class, :unlock, :unlock)
+        stub.unlock('example4')
+      end
     end
   end
 end
diff --git a/spec/etcdv3/namespace/lock_spec.rb b/spec/etcdv3/namespace/lock_spec.rb
index 784ce2f..e976181 100644
--- a/spec/etcdv3/namespace/lock_spec.rb
+++ b/spec/etcdv3/namespace/lock_spec.rb
@@ -2,22 +2,41 @@
 
 # Locking is not implemented in etcd v3.1.X
 unless $instance.version < Gem::Version.new("3.2.0")
-  describe Etcdv3::Lock do
+  describe Etcdv3::Namespace::Lock do
     let(:stub) { local_namespace_stub(Etcdv3::Namespace::Lock, 1, '/namespace/') }
     let(:lease_stub) { local_stub(Etcdv3::Lease, 1) }
 
-    it_should_behave_like "a method with a GRPC timeout", described_class, :unlock, :unlock, 'foo'
+    # NOTE: this was running duplicate tests against Etcdv3::Lock before, but it
+    # doesn't work with Etcdv3::Namespace::Lock
+    #
+    # it_should_behave_like "a method with a GRPC timeout", described_class, :unlock, :unlock, 'foo'
+
     # it_should_behave_like "a method with a GRPC timeout", described_class, :lock, :lock, 'foo'
 
     describe '#lock' do
-      let(:lease_id) { lease_stub.lease_grant(10)['ID'] }
-      subject { stub.lock('foo', lease_id) }
-      it { is_expected.to be_an_instance_of(V3lockpb::LockResponse) }
+      it 'returns a response' do
+        lease_id = lease_stub.lease_grant(10)['ID']
+        expect(stub.lock('example1', lease_id)).to(
+          be_an_instance_of(V3lockpb::LockResponse)
+        )
+      end
+
+      it 'passes metadata correctly' do
+        lease_id = lease_stub.lease_grant(10)['ID']
+        stub = expect_metadata_passthrough_namespace(described_class, :lock, :lock, '/namespace/')
+        stub.lock('example2', lease_id)
+      end
     end
 
     describe '#unlock' do
-      subject { stub.unlock('foo') }
-      it { is_expected.to be_an_instance_of(V3lockpb::UnlockResponse) }
+      it 'returns a response' do
+        expect(stub.unlock('example3')).to be_an_instance_of(V3lockpb::UnlockResponse)
+      end
+
+      it 'passes metadata correctly' do
+        stub = expect_metadata_passthrough_namespace(described_class, :unlock, :unlock, '/namespace/')
+        stub.unlock('example4')
+      end
     end
   end
 end
diff --git a/spec/helpers/connections.rb b/spec/helpers/connections.rb
index 00081b5..ce626ed 100644
--- a/spec/helpers/connections.rb
+++ b/spec/helpers/connections.rb
@@ -21,10 +21,18 @@ def local_stub(interface, timeout=nil)
       interface.new(local_url, :this_channel_is_insecure, timeout, {})
     end
 
+    def local_stub_with_metadata(interface, timeout: nil, metadata: {})
+      interface.new(local_url, :this_channel_is_insecure, timeout, metadata)
+    end
+
     def local_namespace_stub(interface, timeout=nil, namespace)
       interface.new(local_url, :this_channel_is_insecure, timeout, namespace, {})
     end
 
+    def local_namespace_stub_with_metadata(interface, timeout: nil, namespace:, metadata: {})
+      interface.new(local_url, :this_channel_is_insecure, timeout, namespace, metadata)
+    end
+
     def local_url
       "127.0.0.1:#{port}"
     end
diff --git a/spec/helpers/metadata_passthrough.rb b/spec/helpers/metadata_passthrough.rb
new file mode 100644
index 0000000..57f2d84
--- /dev/null
+++ b/spec/helpers/metadata_passthrough.rb
@@ -0,0 +1,21 @@
+module Helpers
+  module MetadataPassthrough
+    include Connections
+
+    def expect_metadata_passthrough(stub_class, method_name, expectation_target)
+      metadata = { user: "foo", password: "bar" }
+      handler = local_stub_with_metadata(stub_class, metadata: metadata, timeout: 1)
+      inner_stub = handler.instance_variable_get("@stub")
+      expect(inner_stub).to receive(expectation_target).with(anything, hash_including(metadata: metadata)).and_call_original
+      return handler
+    end
+
+    def expect_metadata_passthrough_namespace(stub_class, method_name, expectation_target, namespace)
+      metadata = { user: "foo", password: "bar" }
+      handler = local_namespace_stub_with_metadata(stub_class, metadata: metadata, timeout: 1, namespace: namespace)
+      inner_stub = handler.instance_variable_get("@stub")
+      expect(inner_stub).to receive(expectation_target).with(anything, hash_including(metadata: metadata)).and_call_original
+      return handler
+    end
+  end
+end
diff --git a/spec/helpers/test_instance.rb b/spec/helpers/test_instance.rb
index b6bf525..d4fde29 100644
--- a/spec/helpers/test_instance.rb
+++ b/spec/helpers/test_instance.rb
@@ -3,10 +3,12 @@
 require 'socket'
 require 'timeout'
 require 'helpers/connections'
+require 'helpers/metadata_passthrough'
 
 module Helpers
   class TestInstance
     include Helpers::Connections
+    include Helpers::MetadataPassthrough
 
     class InvalidVersionException < StandardError; end
     class PortInUseException < StandardError; end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 125b885..885f54e 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -11,12 +11,14 @@
 require 'etcdv3'
 require 'helpers/test_instance'
 require 'helpers/connections'
+require 'helpers/metadata_passthrough'
 require 'helpers/shared_examples_for_timeout'
 
 $instance = Helpers::TestInstance.new
 
 RSpec.configure do |config|
   config.include(Helpers::Connections)
+  config.include(Helpers::MetadataPassthrough)
 
   config.expect_with :rspec do |expectations|
     expectations.include_chain_clauses_in_custom_matcher_descriptions = true