diff --git a/lib/convertkit/connection.rb b/lib/convertkit/connection.rb
index 9c78096..6c3cd69 100644
--- a/lib/convertkit/connection.rb
+++ b/lib/convertkit/connection.rb
@@ -53,7 +53,8 @@ def default_headers(options)
 
     def process_request(method, params)
       return params if method == :get
-      return params if params.empty?
+      # Faraday writes the body verbatim, so an empty payload still has to be a String.
+      return '' if params.empty?
 
       JSON.generate(params)
     end
diff --git a/lib/convertkit/resources/broadcasts.rb b/lib/convertkit/resources/broadcasts.rb
index fd421c8..b54bfa6 100644
--- a/lib/convertkit/resources/broadcasts.rb
+++ b/lib/convertkit/resources/broadcasts.rb
@@ -80,7 +80,7 @@ def update(id, options= {})
       # See https://developers.convertkit.com/#destroy-a-broadcast for details.
       # @param id [Integer] The id of the broadcast to delete.
       def delete(id)
-        response = @client.delete("#{PATH}/#{id}")
+        response = @client.delete("#{PATH}/#{id}", '', true)
 
         response.success?
       end
diff --git a/lib/convertkit/resources/custom_fields.rb b/lib/convertkit/resources/custom_fields.rb
index 96acda1..19f6778 100644
--- a/lib/convertkit/resources/custom_fields.rb
+++ b/lib/convertkit/resources/custom_fields.rb
@@ -48,7 +48,7 @@ def update(id, label)
       # See https://developers.convertkit.com/#destroy-field for details
       # @param [Integer] id The id of the custom field to delete
       def delete(id)
-        response = @client.delete("#{PATH}/#{id}")
+        response = @client.delete("#{PATH}/#{id}", '', true)
 
         response.success?
       end
diff --git a/spec/lib/convertkit/connection_spec.rb b/spec/lib/convertkit/connection_spec.rb
index e63078e..d4a73f6 100644
--- a/spec/lib/convertkit/connection_spec.rb
+++ b/spec/lib/convertkit/connection_spec.rb
@@ -42,6 +42,13 @@
 
       ConvertKit::Connection.new(url).post('test_path', {hash: 'request_hash'})
     end
+
+    it 'sends an empty body when no params are given' do
+      expect(connection).to receive(:post).with('test_path', '').and_return(response)
+      allow(env).to receive(:body=).with({"message" => "response_hash"})
+
+      ConvertKit::Connection.new(url).post('test_path')
+    end
   end
 
   describe '#post_form' do
@@ -93,6 +100,17 @@
 
       ConvertKit::Connection.new(url).delete('test_path', {hash: 'request_hash'})
     end
+
+    it 'sends an empty body when no params are given' do
+      expect_any_instance_of(Faraday::Connection).to receive(:delete).with('test_path').and_call_original
+      expect(builder).to receive(:build_response) do |connection, request|
+        expect(request.body).to eq('')
+      end.and_return(response)
+
+      allow(env).to receive(:body=).with({"message" => "response_hash"})
+
+      ConvertKit::Connection.new(url).delete('test_path')
+    end
   end
 
   describe '#put' do
@@ -111,6 +129,13 @@
 
       ConvertKit::Connection.new(url).put('test_path', {hash: 'request_hash'})
     end
+
+    it 'sends an empty body when no params are given' do
+      expect(connection).to receive(:put).with('test_path', '').and_return(response)
+      allow(env).to receive(:body=).with({"message" => "response_hash"})
+
+      ConvertKit::Connection.new(url).put('test_path')
+    end
   end
 
   describe 'when the response is not successful' do
diff --git a/spec/lib/convertkit/resources/broadcasts_spec.rb b/spec/lib/convertkit/resources/broadcasts_spec.rb
index a7dfc32..4e3306b 100644
--- a/spec/lib/convertkit/resources/broadcasts_spec.rb
+++ b/spec/lib/convertkit/resources/broadcasts_spec.rb
@@ -150,7 +150,7 @@
     let(:response) { double('response', success?: true) }
 
     it 'deletes a broadcast' do
-      expect(client).to receive(:delete).with('broadcasts/1').and_return(response)
+      expect(client).to receive(:delete).with('broadcasts/1', '', true).and_return(response)
       expect(broadcasts.delete(1)).to be(true)
     end
   end
diff --git a/spec/lib/convertkit/resources/custom_fields_spec.rb b/spec/lib/convertkit/resources/custom_fields_spec.rb
index e2b74ab..4b04ead 100644
--- a/spec/lib/convertkit/resources/custom_fields_spec.rb
+++ b/spec/lib/convertkit/resources/custom_fields_spec.rb
@@ -63,7 +63,7 @@
     let(:response) { double('response', success?: true) }
 
     it 'deletes a custom field' do
-      expect(client).to receive(:delete).with('custom_fields/1').and_return(response)
+      expect(client).to receive(:delete).with('custom_fields/1', '', true).and_return(response)
       expect(custom_fields.delete(1)).to be true
     end
   end