diff --git a/features/cli/debug.feature b/features/cli/debug.feature
new file mode 100644
index 0000000..19f1497
--- /dev/null
+++ b/features/cli/debug.feature
@@ -0,0 +1,5 @@
+Feature: debug CLI option
+
+  Scenario: raises the logger level to DEBUG
+    When I run uhwm with option -d
+    Then the current output must match /log.+debug.+level/i
diff --git a/lib/uh/wm/env.rb b/lib/uh/wm/env.rb
index eab4fc3..b750493 100644
--- a/lib/uh/wm/env.rb
+++ b/lib/uh/wm/env.rb
@@ -3,6 +3,7 @@ module Uh
     class Env
       LOGGER_LEVEL          = Logger::WARN
       LOGGER_LEVEL_VERBOSE  = Logger::INFO
+      LOGGER_LEVEL_DEBUG    = Logger::DEBUG
       LOGGER_LEVEL_STRINGS = %w[DEBUG INFO WARN ERROR FATAL UNKNOWN]
 
       extend Forwardable
@@ -26,7 +27,8 @@ module Uh
 
       def logger
         @logger ||= Logger.new(@output).tap do |o|
-          o.level = verbose? ? LOGGER_LEVEL_VERBOSE : LOGGER_LEVEL
+          o.level = debug? ? LOGGER_LEVEL_DEBUG :
+            verbose? ? LOGGER_LEVEL_VERBOSE : LOGGER_LEVEL
         end
       end
 
diff --git a/spec/uh/wm/env_spec.rb b/spec/uh/wm/env_spec.rb
index 135f831..4b89b04 100644
--- a/spec/uh/wm/env_spec.rb
+++ b/spec/uh/wm/env_spec.rb
@@ -61,9 +61,17 @@ module Uh
         context 'when verbose mode is enabled' do
           before { env.verbose = true }
 
-        it 'has logger level info set' do
-          expect(env.logger.level).to be Logger::INFO
+          it 'has logger level info set' do
+            expect(env.logger.level).to be Logger::INFO
+          end
         end
+
+        context 'when debug mode is enabled' do
+          before { env.debug = true }
+
+          it 'has logger level debug set' do
+            expect(env.logger.level).to be Logger::DEBUG
+          end
         end
       end