diff --git a/lib/pact_broker/string_refinements.rb b/lib/pact_broker/string_refinements.rb
index 677a6ba71..a49e01fb3 100644
--- a/lib/pact_broker/string_refinements.rb
+++ b/lib/pact_broker/string_refinements.rb
@@ -2,7 +2,11 @@ module PactBroker
   module StringRefinements
     refine String do
       def not_blank?
-        self && self.strip.size > 0
+        !blank?
+      end
+
+      def blank?
+        self.strip.size == 0
       end
     end
   end
diff --git a/lib/pact_broker/webhooks/webhook_request_template.rb b/lib/pact_broker/webhooks/webhook_request_template.rb
index b9bff503b..68d930bac 100644
--- a/lib/pact_broker/webhooks/webhook_request_template.rb
+++ b/lib/pact_broker/webhooks/webhook_request_template.rb
@@ -2,6 +2,7 @@
 require 'pact_broker/webhooks/render'
 require 'cgi'
 require 'pact_broker/domain/webhook_request'
+require 'pact_broker/string_refinements'
 
 module PactBroker
   module Webhooks
@@ -9,6 +10,8 @@ class WebhookRequestTemplate
 
       include PactBroker::Logging
       include PactBroker::Messages
+      using PactBroker::StringRefinements
+
       HEADERS_TO_REDACT = [/authorization/i, /token/i]
 
       attr_accessor :method, :url, :headers, :body, :username, :password, :uuid
@@ -31,24 +34,15 @@ def build(template_params)
         attributes = {
           method: http_method,
           url: build_url(template_params),
-          headers: headers,
-          username: username,
-          password: password,
+          headers: build_headers(template_params),
+          username: build_string(username, template_params),
+          password: build_string(password, template_params),
           uuid: uuid,
           body: build_body(template_params)
         }
         PactBroker::Domain::WebhookRequest.new(attributes)
       end
 
-      def build_url(template_params)
-        URI(PactBroker::Webhooks::Render.call(url, template_params){ | value | CGI::escape(value) if !value.nil? } ).to_s
-      end
-
-      def build_body(template_params)
-        body_string = String === body ? body : body.to_json
-        PactBroker::Webhooks::Render.call(body_string, template_params)
-      end
-
       def description
         "#{http_method.upcase} #{URI(url.gsub(PactBroker::Webhooks::Render::TEMPLATE_PARAMETER_REGEXP, 'placeholder')).host}"
       end
@@ -68,11 +62,32 @@ def headers= headers
         @headers = Rack::Utils::HeaderHash.new(headers)
       end
 
-      private
 
       def to_s
         "#{method.upcase} #{url}, username=#{username}, password=#{display_password}, headers=#{redacted_headers}, body=#{body}"
       end
+
+      private
+
+      def build_url(template_params)
+        URI(PactBroker::Webhooks::Render.call(url, template_params){ | value | CGI::escape(value) if !value.nil? } ).to_s
+      end
+
+      def build_body(template_params)
+        body_string = String === body ? body : body.to_json
+        build_string(body_string, template_params)
+      end
+
+      def build_headers(template_params)
+        headers.each_with_object(Rack::Utils::HeaderHash.new) do | (key, value), new_headers |
+          new_headers[key] = build_string(value, template_params)
+        end
+      end
+
+      def build_string(string, template_params)
+        return string if string.nil? || string.blank?
+        PactBroker::Webhooks::Render.call(string, template_params)
+      end
     end
   end
 end
diff --git a/spec/lib/pact_broker/webhooks/webhook_request_template_spec.rb b/spec/lib/pact_broker/webhooks/webhook_request_template_spec.rb
index ad62592da..c78fb8f19 100644
--- a/spec/lib/pact_broker/webhooks/webhook_request_template_spec.rb
+++ b/spec/lib/pact_broker/webhooks/webhook_request_template_spec.rb
@@ -7,11 +7,11 @@ module Webhooks
         {
           method: 'POST',
           url: url,
-          username: "foo",
-          password: "bar",
+          username: "username",
+          password: "password",
           uuid: "1234",
           body: body,
-          headers: {'Foo' => 'bar'}
+          headers: {'headername' => 'headervalue'}
         }
       end
 
@@ -19,11 +19,11 @@ module Webhooks
         {
           method: 'POST',
           url: built_url,
-          username: "foo",
-          password: "bar",
+          username: "usernameBUILT",
+          password: "passwordBUILT",
           uuid: "1234",
           body: built_body,
-          headers: {'Foo' => 'bar'}
+          headers: {'headername' => 'headervalueBUILT'}
         }
       end
 
@@ -73,10 +73,39 @@ module Webhooks
           end
         end
 
+        it "renders each header value" do
+          expect(PactBroker::Webhooks::Render).to receive(:call).with('headervalue', params_hash)
+          subject
+        end
+
+        it "renders the username" do
+          expect(PactBroker::Webhooks::Render).to receive(:call).with('username', params_hash)
+          subject
+        end
+
+        it "renders the password" do
+          expect(PactBroker::Webhooks::Render).to receive(:call).with('password', params_hash)
+          subject
+        end
+
         it "creates a new PactBroker::Domain::WebhookRequest" do
           expect(PactBroker::Domain::WebhookRequest).to receive(:new).with(new_attributes)
           subject
         end
+
+        context "when optional attributes are missing" do
+          let(:attributes) do
+            {
+              method: 'POST',
+              url: url,
+              uuid: "1234",
+            }
+          end
+
+          it "does not blow up" do
+            subject
+          end
+        end
       end
     end
   end