diff --git a/lib/src/core/definitions/form.dart b/lib/src/core/definitions/form.dart
index bd514d4c..425cc8e5 100644
--- a/lib/src/core/definitions/form.dart
+++ b/lib/src/core/definitions/form.dart
@@ -21,7 +21,7 @@ class Form implements Serializable {
   /// An [href] has to be provided. A [contentType] is optional.
   Form(
     this.href, {
-    this.contentType = "application/json",
+    this.contentType = _defaultContentType,
     this.contentCoding,
     this.subprotocol,
     this.security,
@@ -86,6 +86,8 @@ class Form implements Serializable {
     );
   }
 
+  static const _defaultContentType = "application/json";
+
   /// The [href] pointing to the resource.
   ///
   /// Can be a relative or absolute URI.
@@ -134,7 +136,6 @@ class Form implements Serializable {
   Map<String, dynamic> toJson() {
     final result = {
       "href": href.toString(),
-      "contentType": contentType,
       ...additionalFields,
     };
 
@@ -148,6 +149,10 @@ class Form implements Serializable {
           op.map((opValue) => opValue.toString()).toList(growable: false);
     }
 
+    if (contentType != _defaultContentType) {
+      result["contentType"] = contentType;
+    }
+
     if (contentCoding != null) {
       result["contentCoding"] = contentCoding;
     }
diff --git a/test/core/definitions/serialization_test.dart b/test/core/definitions/serialization_test.dart
index 0a7e7f4e..74615d13 100644
--- a/test/core/definitions/serialization_test.dart
+++ b/test/core/definitions/serialization_test.dart
@@ -38,8 +38,6 @@ void main() {
             "op": [
               "readmultipleproperties",
             ],
-            // TODO: Should defaults actually be set?
-            "contentType": "application/json",
           },
         ],
         "properties": {},
@@ -103,7 +101,6 @@ void main() {
         "href": "https://example.org",
         "subprotocol": "foobar",
         "contentCoding": "test",
-        "contentType": "application/json",
         "security": ["test"],
         "response": {
           "contentType": "application/json",
@@ -123,7 +120,6 @@ void main() {
     test("AugmentedForms", () async {
       final formJson = {
         "href": "https://example.org",
-        "contentType": "application/json",
       };
 
       final thingDescription = {
@@ -186,7 +182,6 @@ void main() {
         "forms": [
           {
             "href": "https://example.org",
-            "contentType": "application/json",
           }
         ],
       };