diff --git a/Gemfile.lock b/Gemfile.lock
index f06d00a..2215cb9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    contextual_logger (0.4.0)
+    contextual_logger (0.5.0)
       activesupport
       json
 
diff --git a/contextual_logger.gemspec b/contextual_logger.gemspec
index b06bed3..2f3093c 100644
--- a/contextual_logger.gemspec
+++ b/contextual_logger.gemspec
@@ -2,7 +2,7 @@
 
 Gem::Specification.new do |spec|
   spec.name        = 'contextual_logger'
-  spec.version     = '0.4.0'
+  spec.version     = '0.5.0'
   spec.license     = 'MIT'
   spec.date        = '2018-10-12'
   spec.summary     = 'Add context to your logger'
diff --git a/lib/contextual_logger.rb b/lib/contextual_logger.rb
index 31775c9..4c580ec 100644
--- a/lib/contextual_logger.rb
+++ b/lib/contextual_logger.rb
@@ -9,6 +9,29 @@ class << self
     def new(logger)
       logger.extend(LoggerMixin)
     end
+
+    def normalize_log_level(log_level)
+      if log_level.is_a?(Integer) && (Logger::Severity::DEBUG..Logger::Severity::UNKNOWN).include?(log_level)
+        log_level
+      else
+        case log_level.to_s.downcase
+        when 'debug'
+          Logger::Severity::DEBUG
+        when 'info'
+          Logger::Severity::INFO
+        when 'warn'
+          Logger::Severity::WARN
+        when 'error'
+          Logger::Severity::ERROR
+        when 'fatal'
+          Logger::Severity::FATAL
+        when 'unknown'
+          Logger::Severity::UNKNOWN
+        else
+          raise ArgumentError, "invalid log level: #{log_level.inspect}"
+        end
+      end
+    end
   end
 
   module LoggerMixin
diff --git a/lib/contextual_logger/logger_with_context.rb b/lib/contextual_logger/logger_with_context.rb
index 467100e..38623e0 100644
--- a/lib/contextual_logger/logger_with_context.rb
+++ b/lib/contextual_logger/logger_with_context.rb
@@ -22,27 +22,7 @@ def level
     end
 
     def level=(override_level)
-      @override_level =
-        if (Logger::Severity::DEBUG..Logger::Severity::UNKNOWN).include?(override_level) || override_level.nil?
-          override_level
-        else
-          case override_level.to_s.downcase
-          when 'debug'
-            Logger::Severity::DEBUG
-          when 'info'
-            Logger::Severity::INFO
-          when 'warn'
-            Logger::Severity::WARN
-          when 'error'
-            Logger::Severity::ERROR
-          when 'fatal'
-            Logger::Severity::FATAL
-          when 'unknown'
-            Logger::Severity::UNKNOWN
-          else
-            raise ArgumentError, "invalid log level: #{override_level.inspect}"
-          end
-        end
+      @override_level = (ContextualLogger.normalize_log_level(override_level) if override_level)
     end
 
     def write_entry_to_log(severity, timestamp, progname, message, context:)
diff --git a/spec/lib/contextual_logger_spec.rb b/spec/lib/contextual_logger_spec.rb
index f096a7e..d91f2e9 100644
--- a/spec/lib/contextual_logger_spec.rb
+++ b/spec/lib/contextual_logger_spec.rb
@@ -298,4 +298,57 @@ def expect_log_line_to_be_written(log_line)
       expect(log_stream.string).to match(/\{"message":"info message","severity":"INFO","timestamp":".*"\}/)
     end
   end
+
+  LOG_LEVEL_STRINGS_TO_CONSTANTS =
+  {
+    "DEBUG"   => Logger::Severity::DEBUG,
+    "INFO"    => Logger::Severity::INFO,
+    "WARN"    => Logger::Severity::WARN,
+    "ERROR"   => Logger::Severity::ERROR,
+    "FATAL"   => Logger::Severity::FATAL,
+    "UNKNOWN" => Logger::Severity::UNKNOWN
+  }.freeze
+
+  describe 'module methods' do
+    describe "normalize_log_level" do
+      it "raises an exception on invalid values" do
+        [nil, "", "ABC", 3.5].each do |invalid_value|
+          expect { ContextualLogger.normalize_log_level(invalid_value) }.to raise_exception(ArgumentError, /invalid log level:/), invalid_value
+        end
+      end
+
+      it "accepts Severity constants" do
+        LOG_LEVEL_STRINGS_TO_CONSTANTS.each do |_uppercase_string_level, constant_level|
+          expect(ContextualLogger.normalize_log_level(constant_level)).to eq(constant_level)
+        end
+      end
+
+      it "accepts uppercase strings" do
+        LOG_LEVEL_STRINGS_TO_CONSTANTS.each do |uppercase_string_level, constant_level|
+          expect(ContextualLogger.normalize_log_level(uppercase_string_level)).to eq(constant_level)
+        end
+      end
+
+      it "accepts uppercase symbols" do
+        LOG_LEVEL_STRINGS_TO_CONSTANTS.each do |uppercase_string_level, constant_level|
+          uppercase_symbol_level = uppercase_string_level.to_sym
+          expect(ContextualLogger.normalize_log_level(uppercase_symbol_level)).to eq(constant_level)
+        end
+      end
+
+      it "accepts lowercase strings" do
+        LOG_LEVEL_STRINGS_TO_CONSTANTS.each do |uppercase_string_level, constant_level|
+          lowercase_string_level = uppercase_string_level.downcase
+          expect(ContextualLogger.normalize_log_level(lowercase_string_level)).to eq(constant_level)
+        end
+      end
+
+      it "accepts lowercase symbols" do
+        LOG_LEVEL_STRINGS_TO_CONSTANTS.each do |uppercase_string_level, constant_level|
+          lowercase_symbol_level = uppercase_string_level.downcase.to_sym
+          expect(ContextualLogger.normalize_log_level(lowercase_symbol_level)).to eq(constant_level)
+        end
+      end
+    end
+  end
 end