diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4fda95a..2f05400 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 ## Unreleased
 
 - [#114] Fix user_info endpoint when used in api mode
+- [#112] Add grant_types_supported to discovery response
 
 ## v1.7.2 (2020-05-20)
 
diff --git a/app/controllers/doorkeeper/openid_connect/discovery_controller.rb b/app/controllers/doorkeeper/openid_connect/discovery_controller.rb
index 5b2bbaa..606b842 100644
--- a/app/controllers/doorkeeper/openid_connect/discovery_controller.rb
+++ b/app/controllers/doorkeeper/openid_connect/discovery_controller.rb
@@ -38,16 +38,13 @@ def provider_response
 
           # TODO: support id_token response type
           response_types_supported: doorkeeper.authorization_response_types,
-          response_modes_supported: ['query', 'fragment'],
+          response_modes_supported: %w[query fragment],
+          grant_types_supported: grant_types_supported(doorkeeper),
 
-          token_endpoint_auth_methods_supported: [
-            'client_secret_basic',
-            'client_secret_post',
-
-            # TODO: look into doorkeeper-jwt_assertion for these
-            # 'client_secret_jwt',
-            # 'private_key_jwt'
-          ],
+          # TODO: look into doorkeeper-jwt_assertion for these
+          #  'client_secret_jwt',
+          #  'private_key_jwt'
+          token_endpoint_auth_methods_supported: %w[client_secret_basic client_secret_post],
 
           subject_types_supported: openid_connect.subject_types_supported,
 
@@ -73,6 +70,12 @@ def provider_response
         }.compact
       end
 
+      def grant_types_supported(doorkeeper)
+        grant_types_supported = doorkeeper.grant_flows
+        grant_types_supported << 'refresh_token' if doorkeeper.refresh_token_enabled?
+        grant_types_supported
+      end
+
       def webfinger_response
         {
           subject: params.require(:resource),
diff --git a/spec/controllers/discovery_controller_spec.rb b/spec/controllers/discovery_controller_spec.rb
index 887a802..ac738de 100644
--- a/spec/controllers/discovery_controller_spec.rb
+++ b/spec/controllers/discovery_controller_spec.rb
@@ -20,12 +20,10 @@
         'scopes_supported' => ['openid'],
 
         'response_types_supported' => ['code'],
-        'response_modes_supported' => ['query', 'fragment'],
+        'response_modes_supported' => %w[query fragment],
+        'grant_types_supported' => %w[authorization_code client_credentials],
 
-        'token_endpoint_auth_methods_supported' => [
-          'client_secret_basic',
-          'client_secret_post',
-        ],
+        'token_endpoint_auth_methods_supported' => %w[client_secret_basic client_secret_post],
 
         'subject_types_supported' => [
           'public',
@@ -57,6 +55,17 @@
       }.sort)
     end
 
+    context 'when refresh_token grant type is enabled' do
+      before { Doorkeeper.configure { use_refresh_token } }
+
+      it 'add refresh_token to grant_types_supported' do
+        get :provider
+        data = JSON.parse(response.body)
+
+        expect(data['grant_types_supported']).to eq %w[authorization_code client_credentials refresh_token]
+      end
+    end
+
     it 'uses the protocol option for generating URLs' do
       Doorkeeper::OpenidConnect.configure do
         protocol { :testing }