diff --git a/lib/instapaper/error.rb b/lib/instapaper/error.rb
index 7be4bcd..38a7eb1 100644
--- a/lib/instapaper/error.rb
+++ b/lib/instapaper/error.rb
@@ -11,6 +11,7 @@ module Instapaper
     OAuthError = Class.new(self)
 
     ERRORS = {
+      401  => 'Unauthorized',
       1040 => 'Rate-limit exceeded',
       1041 => 'Premium account required',
       1042 => 'Application is suspended',
diff --git a/lib/instapaper/http/request.rb b/lib/instapaper/http/request.rb
index 1c0c030..31a3a26 100644
--- a/lib/instapaper/http/request.rb
+++ b/lib/instapaper/http/request.rb
@@ -49,13 +49,19 @@ module Instapaper
       end
 
       def fail_if_error_response_code(response)
-        fail Instapaper::Error::ServiceUnavailableError if response.status != 200
+        return if response.status == 200
+
+        if Instapaper::Error::CODES.include?(response.status.code)
+          fail Instapaper::Error.from_response(response.status.code, @path)
+        else
+          fail Instapaper::Error::ServiceUnavailableError
+        end
       end
 
       def fail_if_error_unparseable_response(response)
         response.parse(:json)
       rescue JSON::ParserError
-        raise Instapaper::Error::ServiceUnavailableError
+        fail Instapaper::Error::ServiceUnavailableError
       end
 
       def fail_if_error_in_body(response)
diff --git a/spec/instapaper/error_spec.rb b/spec/instapaper/error_spec.rb
index d383119..5f914d4 100644
--- a/spec/instapaper/error_spec.rb
+++ b/spec/instapaper/error_spec.rb
@@ -70,4 +70,14 @@ describe Instapaper::Error do
       end
     end
   end
+
+  context 'HTTP errors' do
+    before do
+      stub_post('/api/1.1/oauth/access_token')
+        .to_return(status: 401, body: 'Unauthorized', headers: {})
+    end
+    it 'raises an Instapaper::Error' do
+      expect { @client.access_token('foo', 'bar') }.to raise_error(Instapaper::Error)
+    end
+  end
 end