diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9ac92501..5cd51b67 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+### Unreleased
+* Fixed HTTParty content type issue when request body is nil - POST, PUT, PATCH, and DELETE now default to empty object to ensure Content-Type: application/json is sent (#536)
+* Added support for request_body parameter on DELETE (e.g. cancellation_reason for bookings) (#536)
+
 ### [6.7.1]
 * Fix large attachment handling with string keys and custom content_ids
 
diff --git a/lib/nylas/handler/api_operations.rb b/lib/nylas/handler/api_operations.rb
index b1d59560..873ba423 100644
--- a/lib/nylas/handler/api_operations.rb
+++ b/lib/nylas/handler/api_operations.rb
@@ -63,6 +63,7 @@ module Post
       # @param path [String] Destination path for the call.
       # @param query_params [Hash, {}] Query params to pass to the call.
       # @param request_body [Hash, nil] Request body to pass to the call.
+      #   Defaults to {} when nil to ensure Content-Type: application/json is sent.
       # @param headers [Hash, {}] Additional HTTP headers to include in the payload.
       # @return [Array(Hash, String, Hash)] Nylas data object, API Request ID, and response headers.
       def post(path:, query_params: {}, request_body: nil, headers: {})
@@ -70,7 +71,7 @@ def post(path:, query_params: {}, request_body: nil, headers: {})
           method: :post,
           path: path,
           query: query_params,
-          payload: request_body,
+          payload: request_body || {},
           headers: headers,
           api_key: api_key,
           timeout: timeout
@@ -90,6 +91,7 @@ module Put
       # @param path [String] Destination path for the call.
       # @param query_params [Hash, {}] Query params to pass to the call.
       # @param request_body [Hash, nil] Request body to pass to the call.
+      #   Defaults to {} when nil to ensure Content-Type: application/json is sent.
       # @param headers [Hash, {}] Additional HTTP headers to include in the payload.
       # @return Nylas data object and API Request ID.
       def put(path:, query_params: {}, request_body: nil, headers: {})
@@ -97,7 +99,7 @@ def put(path:, query_params: {}, request_body: nil, headers: {})
           method: :put,
           path: path,
           query: query_params,
-          payload: request_body,
+          payload: request_body || {},
           headers: headers,
           api_key: api_key,
           timeout: timeout
@@ -117,6 +119,7 @@ module Patch
       # @param path [String] Destination path for the call.
       # @param query_params [Hash, {}] Query params to pass to the call.
       # @param request_body [Hash, nil] Request body to pass to the call.
+      #   Defaults to {} when nil to ensure Content-Type: application/json is sent.
       # @param headers [Hash, {}] Additional HTTP headers to include in the payload.
       # @return Nylas data object and API Request ID.
       def patch(path:, query_params: {}, request_body: nil, headers: {})
@@ -124,7 +127,7 @@ def patch(path:, query_params: {}, request_body: nil, headers: {})
           method: :patch,
           path: path,
           query: query_params,
-          payload: request_body,
+          payload: request_body || {},
           headers: headers,
           api_key: api_key,
           timeout: timeout
@@ -143,15 +146,17 @@ module Delete
       #
       # @param path [String] Destination path for the call.
       # @param query_params [Hash, {}] Query params to pass to the call.
+      # @param request_body [Hash, nil] Optional request body (e.g. cancellation_reason for bookings).
+      #   Defaults to {} to ensure Content-Type: application/json is sent.
       # @param headers [Hash, {}] Additional HTTP headers to include in the payload.
       # @return Nylas data object and API Request ID.
-      def delete(path:, query_params: {}, headers: {})
+      def delete(path:, query_params: {}, request_body: nil, headers: {})
         response = execute(
           method: :delete,
           path: path,
           query: query_params,
           headers: headers,
-          payload: nil,
+          payload: request_body || {},
           api_key: api_key,
           timeout: timeout
         )
diff --git a/lib/nylas/resources/bookings.rb b/lib/nylas/resources/bookings.rb
index e357fc73..62406381 100644
--- a/lib/nylas/resources/bookings.rb
+++ b/lib/nylas/resources/bookings.rb
@@ -64,11 +64,13 @@ def confirm(booking_id:, request_body:, query_params: nil)
     # Delete a booking.
     # @param booking_id [String] The id of the booking to delete.
     # @param query_params [Hash, nil] Query params to pass to the request.
+    # @param request_body [Hash, nil] Optional body params (e.g. cancellation_reason).
     # @return [Array(TrueClass, String)] True and the API Request ID for the delete operation.
-    def destroy(booking_id:, query_params: nil)
+    def destroy(booking_id:, query_params: nil, request_body: nil)
       _, request_id = delete(
         path: "#{api_uri}/v3/scheduling/bookings/#{booking_id}",
-        query_params: query_params
+        query_params: query_params,
+        request_body: request_body
       )
 
       [true, request_id]
diff --git a/spec/nylas/handler/api_operations_spec.rb b/spec/nylas/handler/api_operations_spec.rb
index df6c5739..bb12dfe9 100644
--- a/spec/nylas/handler/api_operations_spec.rb
+++ b/spec/nylas/handler/api_operations_spec.rb
@@ -143,7 +143,7 @@ def initialize(api_key, api_uri, timeout)
           method: :post,
           path: path,
           query: {},
-          payload: nil,
+          payload: {},
           headers: {},
           api_key: api_key,
           timeout: timeout
@@ -164,7 +164,7 @@ def initialize(api_key, api_uri, timeout)
           method: :post,
           path: path,
           query: {},
-          payload: nil,
+          payload: {},
           headers: {},
           api_key: api_key,
           timeout: timeout
@@ -174,6 +174,22 @@ def initialize(api_key, api_uri, timeout)
 
         expect(response).to eq([mock_response[:data], mock_response[:request_id], nil])
       end
+
+      it "passes request_body to execute when provided" do
+        path = "#{api_uri}/path"
+        request_body = { foo: "bar" }
+        allow(api_operations).to receive(:execute).with(
+          method: :post,
+          path: path,
+          query: {},
+          payload: request_body,
+          headers: {},
+          api_key: api_key,
+          timeout: timeout
+        ).and_return(mock_response)
+
+        api_operations.send(:post, path: path, request_body: request_body)
+      end
     end
   end
 
@@ -206,7 +222,7 @@ def initialize(api_key, api_uri, timeout)
           method: :put,
           path: path,
           query: {},
-          payload: nil,
+          payload: {},
           headers: {},
           api_key: api_key,
           timeout: timeout
@@ -216,6 +232,22 @@ def initialize(api_key, api_uri, timeout)
 
         expect(response).to eq([mock_response[:data], mock_response[:request_id]])
       end
+
+      it "passes request_body to execute when provided" do
+        path = "#{api_uri}/path"
+        request_body = { foo: "bar" }
+        allow(api_operations).to receive(:execute).with(
+          method: :put,
+          path: path,
+          query: {},
+          payload: request_body,
+          headers: {},
+          api_key: api_key,
+          timeout: timeout
+        ).and_return(mock_response)
+
+        api_operations.send(:put, path: path, request_body: request_body)
+      end
     end
   end
 
@@ -248,7 +280,7 @@ def initialize(api_key, api_uri, timeout)
           method: :patch,
           path: path,
           query: {},
-          payload: nil,
+          payload: {},
           headers: {},
           api_key: api_key,
           timeout: timeout
@@ -258,6 +290,22 @@ def initialize(api_key, api_uri, timeout)
 
         expect(response).to eq([mock_response[:data], mock_response[:request_id]])
       end
+
+      it "passes request_body to execute when provided" do
+        path = "#{api_uri}/path"
+        request_body = { foo: "bar" }
+        allow(api_operations).to receive(:execute).with(
+          method: :patch,
+          path: path,
+          query: {},
+          payload: request_body,
+          headers: {},
+          api_key: api_key,
+          timeout: timeout
+        ).and_return(mock_response)
+
+        api_operations.send(:patch, path: path, request_body: request_body)
+      end
     end
   end
 
@@ -271,7 +319,7 @@ def initialize(api_key, api_uri, timeout)
           method: :delete,
           path: path,
           query: query_params,
-          payload: nil,
+          payload: {},
           headers: headers,
           api_key: api_key,
           timeout: timeout
@@ -288,7 +336,7 @@ def initialize(api_key, api_uri, timeout)
           method: :delete,
           path: path,
           query: {},
-          payload: nil,
+          payload: {},
           headers: {},
           api_key: api_key,
           timeout: timeout
@@ -298,6 +346,22 @@ def initialize(api_key, api_uri, timeout)
 
         expect(response).to eq([mock_response[:data], mock_response[:request_id]])
       end
+
+      it "passes request_body to execute when provided" do
+        path = "#{api_uri}/path"
+        request_body = { cancellation_reason: "Meeting cancelled" }
+        allow(api_operations).to receive(:execute).with(
+          method: :delete,
+          path: path,
+          query: {},
+          payload: request_body,
+          headers: {},
+          api_key: api_key,
+          timeout: timeout
+        ).and_return(mock_response)
+
+        api_operations.send(:delete, path: path, request_body: request_body)
+      end
     end
   end
 end
diff --git a/spec/nylas/handler/http_client_integration_spec.rb b/spec/nylas/handler/http_client_integration_spec.rb
index d26be56a..7fea2420 100644
--- a/spec/nylas/handler/http_client_integration_spec.rb
+++ b/spec/nylas/handler/http_client_integration_spec.rb
@@ -75,6 +75,46 @@ class TestHttpClientIntegration
     end
   end
 
+  describe "Integration Tests - Content-Type for body-less requests (HTTParty fix)" do
+    it "sends Content-Type: application/json for POST with empty payload" do
+      stub_request(:post, "https://test.api.nylas.com/v3/connect/revoke")
+        .with(
+          body: "{}",
+          headers: { "Content-Type" => "application/json" }
+        )
+        .to_return(status: 200, body: "{}", headers: { "Content-Type" => "application/json" })
+
+      http_client.send(:execute,
+                       method: :post,
+                       path: "https://test.api.nylas.com/v3/connect/revoke",
+                       timeout: 30,
+                       payload: {},
+                       api_key: "fake-key")
+
+      expect(WebMock).to have_requested(:post, "https://test.api.nylas.com/v3/connect/revoke")
+        .with(headers: { "Content-Type" => "application/json" }, body: "{}")
+    end
+
+    it "sends Content-Type: application/json for DELETE with empty payload" do
+      stub_request(:delete, "https://test.api.nylas.com/v3/scheduling/bookings/booking-123")
+        .with(
+          body: "{}",
+          headers: { "Content-Type" => "application/json" }
+        )
+        .to_return(status: 200, body: "{}", headers: { "Content-Type" => "application/json" })
+
+      http_client.send(:execute,
+                       method: :delete,
+                       path: "https://test.api.nylas.com/v3/scheduling/bookings/booking-123",
+                       timeout: 30,
+                       payload: {},
+                       api_key: "fake-key")
+
+      expect(WebMock).to have_requested(:delete, "https://test.api.nylas.com/v3/scheduling/bookings/booking-123")
+        .with(headers: { "Content-Type" => "application/json" }, body: "{}")
+    end
+  end
+
   describe "Integration Tests - backwards compatibility" do
     it "maintains the same response format as rest-client" do
       response_json = { "data" => { "id" => "123", "name" => "test" } }
diff --git a/spec/nylas/handler/http_client_spec.rb b/spec/nylas/handler/http_client_spec.rb
index a5d79ff8..9edb9c23 100644
--- a/spec/nylas/handler/http_client_spec.rb
+++ b/spec/nylas/handler/http_client_spec.rb
@@ -126,6 +126,17 @@ class TestHttpClient
     end
 
     context "when building request with a payload" do
+      it "returns the correct request with empty json payload and sets Content-Type" do
+        payload = {}
+        request = http_client.send(:build_request, method: :post, path: "https://test.api.nylas.com/foo",
+                                                   payload: payload, api_key: "fake-key")
+
+        expect(request[:method]).to eq(:post)
+        expect(request[:url]).to eq("https://test.api.nylas.com/foo")
+        expect(request[:payload]).to eq("{}")
+        expect(request[:headers]).to include("Content-type" => "application/json")
+      end
+
       it "returns the correct request with a json payload" do
         payload = { foo: "bar" }
         request = http_client.send(:build_request, method: :post, path: "https://test.api.nylas.com/foo",
diff --git a/spec/nylas/resources/bookings_spec.rb b/spec/nylas/resources/bookings_spec.rb
index 79311258..5205a3d2 100644
--- a/spec/nylas/resources/bookings_spec.rb
+++ b/spec/nylas/resources/bookings_spec.rb
@@ -185,7 +185,7 @@
       booking_id = "booking-123"
       path = "#{api_uri}/v3/scheduling/bookings/#{booking_id}"
       allow(bookings).to receive(:delete)
-        .with(path: path, query_params: nil)
+        .with(path: path, query_params: nil, request_body: nil)
         .and_return(delete_response)
 
       bookings_response = bookings.destroy(booking_id: booking_id)
@@ -197,11 +197,26 @@
       query_params = { "foo": "bar" }
       path = "#{api_uri}/v3/scheduling/bookings/#{booking_id}"
       allow(bookings).to receive(:delete)
-        .with(path: path, query_params: query_params)
+        .with(path: path, query_params: query_params, request_body: nil)
         .and_return(delete_response)
 
       bookings_response = bookings.destroy(booking_id: booking_id, query_params: query_params)
       expect(bookings_response).to eq(delete_response)
     end
+
+    it "calls the delete method with request_body for cancellation_reason" do
+      booking_id = "booking-123"
+      request_body = { cancellation_reason: "Meeting no longer needed" }
+      path = "#{api_uri}/v3/scheduling/bookings/#{booking_id}"
+      allow(bookings).to receive(:delete)
+        .with(path: path, query_params: nil, request_body: request_body)
+        .and_return(delete_response)
+
+      bookings_response = bookings.destroy(
+        booking_id: booking_id,
+        request_body: request_body
+      )
+      expect(bookings_response).to eq(delete_response)
+    end
   end
 end