diff --git a/resources/zeebe.json b/resources/zeebe.json
index 9216911..f368c3d 100644
--- a/resources/zeebe.json
+++ b/resources/zeebe.json
@@ -292,9 +292,26 @@
           "name": "formId",
           "type": "String",
           "isAttr": true
+        },
+        {
+          "name": "externalReference",
+          "type": "String",
+          "isAttr": true
         }
       ]
     },
+    {
+      "name": "UserTask",
+      "superClass": [
+        "Element"
+      ],
+      "meta": {
+        "allowedIn": [
+          "bpmn:UserTask"
+        ]
+      },
+      "properties": []
+    },
     {
       "name": "CalledDecision",
       "superClass": [
diff --git a/test/fixtures/xml/userTask-zeebe-formDefinition-externalReference.part.bpmn b/test/fixtures/xml/userTask-zeebe-formDefinition-externalReference.part.bpmn
new file mode 100644
index 0000000..522fe61
--- /dev/null
+++ b/test/fixtures/xml/userTask-zeebe-formDefinition-externalReference.part.bpmn
@@ -0,0 +1,9 @@
+<bpmn:userTask 
+  id="user-task-1" 
+  xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL"
+  xmlns:zeebe="http://camunda.org/schema/zeebe/1.0"
+>
+  <bpmn:extensionElements>
+    <zeebe:formDefinition externalReference="form-1" />
+  </bpmn:extensionElements>
+</bpmn:userTask>
\ No newline at end of file
diff --git a/test/fixtures/xml/userTask-zeebe-formDefinition.bpmn b/test/fixtures/xml/userTask-zeebe-formDefinition.bpmn
new file mode 100644
index 0000000..34efb66
--- /dev/null
+++ b/test/fixtures/xml/userTask-zeebe-formDefinition.bpmn
@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<bpmn:definitions xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:zeebe="http://camunda.org/schema/zeebe/1.0" id="Definitions_1igmezy" targetNamespace="http://bpmn.io/schema/bpmn" exporter="Zeebe Modeler" exporterVersion="0.9.1">
+  <bpmn:process id="Process_17v88t0" isExecutable="true">
+    <bpmn:userTask id="Activity_1naoqum" name="Job Worker User Task">
+      <bpmn:extensionElements>
+        <zeebe:formDefinition formId="form" />
+      </bpmn:extensionElements>
+    </bpmn:userTask>
+    <bpmn:userTask id="UserTask" name="Zeebe User Task">
+      <bpmn:extensionElements>
+        <zeebe:formDefinition externalReference="form-1" />
+        <zeebe:userTask />
+      </bpmn:extensionElements>
+    </bpmn:userTask>
+  </bpmn:process>
+  <bpmndi:BPMNDiagram id="BPMNDiagram_1">
+    <bpmndi:BPMNPlane id="BPMNPlane_1" bpmnElement="Process_17v88t0">
+      <bpmndi:BPMNShape id="Activity_10g169d_di" bpmnElement="Activity_1naoqum">
+        <dc:Bounds x="270" y="80" width="100" height="80" />
+      </bpmndi:BPMNShape>
+      <bpmndi:BPMNShape id="UserTask_di" bpmnElement="UserTask">
+        <dc:Bounds x="270" y="180" width="100" height="80" />
+      </bpmndi:BPMNShape>
+    </bpmndi:BPMNPlane>
+  </bpmndi:BPMNDiagram>
+</bpmn:definitions>
diff --git a/test/fixtures/xml/userTask-zeebe-userTask.part.bpmn b/test/fixtures/xml/userTask-zeebe-userTask.part.bpmn
new file mode 100644
index 0000000..74ea34b
--- /dev/null
+++ b/test/fixtures/xml/userTask-zeebe-userTask.part.bpmn
@@ -0,0 +1,9 @@
+<bpmn:userTask
+  id="user-task-1"
+  xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL"
+  xmlns:zeebe="http://camunda.org/schema/zeebe/1.0"
+>
+  <bpmn:extensionElements>
+    <zeebe:userTask />
+  </bpmn:extensionElements>
+</bpmn:userTask>
diff --git a/test/spec/xml/read.js b/test/spec/xml/read.js
index 167f054..c50bcba 100644
--- a/test/spec/xml/read.js
+++ b/test/spec/xml/read.js
@@ -582,11 +582,66 @@ describe('read', function() {
           });
         });
 
+
+        it('zeebe:externalReference', async function() {
+
+          // given
+          var xml = readFile('test/fixtures/xml/userTask-zeebe-formDefinition-externalReference.part.bpmn');
+
+          // when
+          const {
+            rootElement: proc
+          } = await moddle.fromXML(xml, 'bpmn:UserTask');
+
+          // then
+          expect(proc).to.jsonEqual({
+            $type: 'bpmn:UserTask',
+            id: 'user-task-1',
+            extensionElements: {
+              $type: 'bpmn:ExtensionElements',
+              values: [
+                {
+                  $type: 'zeebe:FormDefinition',
+                  externalReference: 'form-1'
+                }
+              ]
+            }
+          });
+        });
       });
 
     });
 
 
+    describe('zeebe:userTask', function() {
+
+      it('should read', async function() {
+
+        // given
+        var xml = readFile('test/fixtures/xml/userTask-zeebe-userTask.part.bpmn');
+
+        // when
+        const {
+          rootElement: proc
+        } = await moddle.fromXML(xml, 'bpmn:UserTask');
+
+        // then
+        expect(proc).to.jsonEqual({
+          $type: 'bpmn:UserTask',
+          id: 'user-task-1',
+          extensionElements: {
+            $type: 'bpmn:ExtensionElements',
+            values: [
+              {
+                $type: 'zeebe:UserTask'
+              }
+            ]
+          }
+        });
+      });
+    });
+
+
     describe('zeebe:calledDecision', function() {
 
       it('on BusinessRuleTask', async function() {
diff --git a/test/spec/xml/roundtrip.js b/test/spec/xml/roundtrip.js
index 81cea6f..04583b8 100644
--- a/test/spec/xml/roundtrip.js
+++ b/test/spec/xml/roundtrip.js
@@ -54,4 +54,10 @@ describe('import -> export roundtrip', function() {
 
 
   it('should keep zeebe:modelerTemplate', validateExport('test/fixtures/xml/rootElement.bpmn'));
+
+
+  describe('userTask', function() {
+
+    it('should keep zeebe:formDefinition properties', validateExport('test/fixtures/xml/userTask-zeebe-formDefinition.bpmn'));
+  });
 });
diff --git a/test/spec/xml/write.js b/test/spec/xml/write.js
index 1994180..c0c6d89 100644
--- a/test/spec/xml/write.js
+++ b/test/spec/xml/write.js
@@ -281,6 +281,50 @@ describe('write', function() {
         expect(xml).to.eql(expectedXML);
       });
 
+
+      it('zeebe:externalReference', async function() {
+
+        // given
+        var proc = moddle.create('bpmn:UserTask', {
+          extensionElements: moddle.create('bpmn:ExtensionElements', {
+            values: [
+              moddle.create('zeebe:FormDefinition', {
+                externalReference: 'form-1'
+              })
+            ]
+          })
+        });
+
+        var expectedXML =
+          '<bpmn:userTask xmlns:bpmn="http://www.omg.org/spec/BPMN/20100524/MODEL" ' +
+                         'xmlns:zeebe="http://camunda.org/schema/zeebe/1.0">' +
+            '<bpmn:extensionElements>' +
+              '<zeebe:formDefinition externalReference="form-1" />' +
+            '</bpmn:extensionElements>' +
+          '</bpmn:userTask>';
+
+        // when
+        const xml = await write(proc);
+
+        // then
+        expect(xml).to.eql(expectedXML);
+      });
+    });
+
+
+    it('zeebe:userTask', async function() {
+
+      // given
+      var userTask = moddle.create('zeebe:UserTask', {});
+
+      var expectedXML = '<zeebe:userTask ' +
+        'xmlns:zeebe="http://camunda.org/schema/zeebe/1.0" />';
+
+      // when
+      const xml = await write(userTask);
+
+      // then
+      expect(xml).to.eql(expectedXML);
     });