diff --git a/index.js b/index.js
index 77d5b1bf..ccddceb0 100644
--- a/index.js
+++ b/index.js
@@ -40,8 +40,7 @@ async function run() {
       throw new Error('Invalid task definition: Could not find container definition with matching name');
     }
     containerDef.image = imageURI;
-    containerDef.executionRoleArn = taskRoleArn;
-    containerDef.taskRoleArn = executionRoleArn;
+
 
     if (command) {
       containerDef.command = command.split(' ')
@@ -126,6 +125,14 @@ async function run() {
       })
     }
 
+    if (taskRoleArn) {
+      taskDefContents.taskRoleArn = taskRoleArn;
+    }
+
+    if (executionRoleArn) {
+      taskDefContents.executionRoleArn = executionRoleArn;
+    }
+
     // Write out a new task definition file
     var updatedTaskDefFile = tmp.fileSync({
       tmpdir: process.env.RUNNER_TEMP,