diff --git a/src/main/java/org/thoughtslive/jenkins/plugins/jira/service/JiraService.java b/src/main/java/org/thoughtslive/jenkins/plugins/jira/service/JiraService.java
index b33cb309..49a8754d 100644
--- a/src/main/java/org/thoughtslive/jenkins/plugins/jira/service/JiraService.java
+++ b/src/main/java/org/thoughtslive/jenkins/plugins/jira/service/JiraService.java
@@ -193,10 +193,15 @@ public ResponseData<Object> updateIssue(final String issueIdOrKey, final Object
     }
   }
 
-  public ResponseData<Void> assignIssue(final String issueIdorKey, final String userName) {
+  public ResponseData<Void> assignIssue(final String issueIdorKey, final String userName,
+      final String accountId) {
     try {
       Map input = Maps.newHashMap();
-      input.put("name", userName);
+      if (userName != null) {
+          input.put("name", userName);
+      } else {
+          input.put("accountId", accountId);
+      }
       return parseResponse(
           jiraEndPoints
               .assignIssue(issueIdorKey, input)
diff --git a/src/main/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStep.java b/src/main/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStep.java
index 4fcaf33a..e046441f 100644
--- a/src/main/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStep.java
+++ b/src/main/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStep.java
@@ -76,10 +76,11 @@ protected ResponseData<Void> run() throws Exception {
       ResponseData<Void> response = verifyInput();
 
       if (response == null) {
-        final String userName = Util.fixEmpty(step.getUserName()) == null ? Util.fixEmpty(step.getAccountId()) : Util.fixEmpty(step.getUserName());
+        final String userName = Util.fixEmpty(step.getUserName());
+        final String accountId =  Util.fixEmpty(step.getAccountId());
         logger.println("JIRA: Site - " + siteName + " - Assigning issue: " + step.getIdOrKey()
-            + " to: " + userName);
-        response = jiraService.assignIssue(step.getIdOrKey(), userName);
+            + " to username: " + userName + " / accountId: " + accountId);
+        response = jiraService.assignIssue(step.getIdOrKey(), userName, accountId);
       }
 
       return logResponse(response);
diff --git a/src/test/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStepTest.java b/src/test/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStepTest.java
index c4bfb1f9..6047d939 100644
--- a/src/test/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStepTest.java
+++ b/src/test/java/org/thoughtslive/jenkins/plugins/jira/steps/AssignIssueStepTest.java
@@ -70,7 +70,7 @@ public void setup() throws IOException, InterruptedException {
     doNothing().when(printStreamMock).println();
 
     final ResponseDataBuilder<Void> builder = ResponseData.builder();
-    when(jiraServiceMock.assignIssue(any(), any()))
+    when(jiraServiceMock.assignIssue(any(), any(), any()))
         .thenReturn(builder.successful(true).code(200).message("Success").build());
 
     when(contextMock.get(Run.class)).thenReturn(runMock);
@@ -99,7 +99,7 @@ public void testWithEmptyUserNameOrAccountIdThrowsAbortException() throws Except
     stepExecution.run();
 
     // Assert Test
-    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", null);
+    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", null, null);
     assertThat(step.isFailOnError()).isEqualTo(true);
   }
 
@@ -112,7 +112,7 @@ public void testSuccessfulUnassignIssue() throws Exception {
     stepExecution.run();
 
     // Assert Test
-    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", null);
+    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", null, null);
     assertThat(step.isFailOnError()).isEqualTo(true);
   }
 
@@ -125,7 +125,7 @@ public void testSuccessfulAssignIssue() throws Exception {
     stepExecution.run();
 
     // Assert Test
-    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", "testUser");
+    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", "testUser", null);
     assertThat(step.isFailOnError()).isEqualTo(true);
   }
 
@@ -138,7 +138,7 @@ public void testSuccessfulAssignIssueByAccountId() throws Exception {
     stepExecution.run();
 
     // Assert Test
-    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", "testUser");
+    verify(jiraServiceMock, times(1)).assignIssue("TEST-1", null, "testUser");
     assertThat(step.isFailOnError()).isEqualTo(true);
   }
 }