diff --git a/src/main/groovy/com/github/lookout/whoas/HookRequest.groovy b/src/main/groovy/com/github/lookout/whoas/HookRequest.groovy
index 0a6d6b8..850b750 100644
--- a/src/main/groovy/com/github/lookout/whoas/HookRequest.groovy
+++ b/src/main/groovy/com/github/lookout/whoas/HookRequest.groovy
@@ -19,7 +19,7 @@ class HookRequest {
     private DateTime deliverAfter
 
     @JsonProperty
-    private String contentTypeParam
+    private String contentType
 
     /** Constructor for Jackson */
     HookRequest() { }
@@ -28,10 +28,10 @@ class HookRequest {
      * Default constructor for creating a simple HookRequest with a URL and the
      * POST data to be delivered to that URL
      */
-    HookRequest(String hookUrl, String hookData, String contentTypeParam) {
+    HookRequest(String hookUrl, String hookData, String contentType) {
         this.retries = 0
         this.url = hookUrl
         this.postData = hookData
-        this.contentTypeParam = contentTypeParam
+        this.contentType = contentType
     }
 }
diff --git a/src/main/groovy/com/github/lookout/whoas/Publisher.groovy b/src/main/groovy/com/github/lookout/whoas/Publisher.groovy
index 216d3b5..5a3b6ef 100644
--- a/src/main/groovy/com/github/lookout/whoas/Publisher.groovy
+++ b/src/main/groovy/com/github/lookout/whoas/Publisher.groovy
@@ -13,6 +13,7 @@ import javax.ws.rs.ProcessingException
  * request logic for Whoas
  */
 class Publisher {
+    private final String DEFAULT_CONTENT_TYPE = 'application/json'
     /** Maximum number of failures we will retry on */
     private final int DEFAULT_MAX_RETRIES = 5
 
@@ -102,7 +103,7 @@ class Publisher {
         return jerseyClient.target(request.url)
                     .request()
                     .buildPost(Entity.entity(request.postData,
-                                             "application/vnd." + request.contentTypeParam + "+json"))
+                                             request.contentType? request.contentType: DEFAULT_CONTENT_TYPE))
     }
 
 }
diff --git a/src/test/groovy/com/github/lookout/whoas/PublisherSpec.groovy b/src/test/groovy/com/github/lookout/whoas/PublisherSpec.groovy
index d0cf1fe..d7d505d 100644
--- a/src/test/groovy/com/github/lookout/whoas/PublisherSpec.groovy
+++ b/src/test/groovy/com/github/lookout/whoas/PublisherSpec.groovy
@@ -49,7 +49,33 @@ class PublisherSpec extends Specification {
         given:
         Invocation inv
         HookRequest request = new HookRequest('http://example.com',
-                                                'magic post data!','appname.event1.v1')
+                                                'magic post data!','application/vnd.appname.event1.v1+json')
+
+        when:
+        inv = publisher.buildInvocationFrom(request)
+
+        then:
+        inv instanceof Invocation
+    }
+
+    def "buildInvocationFrom() should create a valid Jersey Invocation when content type is null"() {
+        given:
+        Invocation inv
+        HookRequest request = new HookRequest('http://example.com',
+                'magic post data!', null)
+
+        when:
+        inv = publisher.buildInvocationFrom(request)
+
+        then:
+        inv instanceof Invocation
+    }
+
+    def "buildInvocationFrom() should create a valid Jersey Invocation when content type is empty"() {
+        given:
+        Invocation inv
+        HookRequest request = new HookRequest('http://example.com',
+                'magic post data!', '')
 
         when:
         inv = publisher.buildInvocationFrom(request)