diff --git a/lib/ably/models/protocol_message.rb b/lib/ably/models/protocol_message.rb
index 07572bb88..1534a135e 100644
--- a/lib/ably/models/protocol_message.rb
+++ b/lib/ably/models/protocol_message.rb
@@ -216,6 +216,11 @@ def has_transient_flag?
       flags & 16 == 16 # 2^4
     end
 
+    # @api private
+    def has_attach_resume_flag?
+      flags & 32 == 32 # 2^5
+    end
+
     # @api private
     def has_attach_presence_flag?
       flags & 65536 == 65536 # 2^16
diff --git a/spec/unit/models/protocol_message_spec.rb b/spec/unit/models/protocol_message_spec.rb
index cdbee41de..53c7a20a6 100644
--- a/spec/unit/models/protocol_message_spec.rb
+++ b/spec/unit/models/protocol_message_spec.rb
@@ -176,6 +176,28 @@ def new_protocol_message(options)
         end
       end
 
+      context 'when attach resumed flag' do
+        context 'flags is 34' do
+          let(:protocol_message) { new_protocol_message(flags: 34) }
+
+          it '#has_attach_resume_flag? is true' do
+            expect(protocol_message.has_attach_resume_flag?).to be_truthy
+          end
+
+          it '#has_attach_presence_flag? is false' do
+            expect(protocol_message.has_attach_presence_flag?).to be_falsey
+          end
+        end
+
+        context 'flags is 0' do
+          let(:protocol_message) { new_protocol_message(flags: 0) }
+
+          it 'should raise an exception if flags is a float number' do
+            expect(protocol_message.has_attach_resume_flag?).to be_falsy
+          end
+        end
+      end
+
       context 'when channel resumed and presence flags present' do
         let(:protocol_message) { new_protocol_message(flags: 5) }