Getting error "At least one of 'memory' or 'memoryReservation' must be specified" on AWS

Question

AWS is giving error "Service:AmazonECS, Code:ClientException, Message:Invalid setting for container 'frontend'. At least one of 'memory' or 'memoryReservation' must be specified" below is dockerrun.aws.json

{
"AWSEBDockerrunVersion": 2,
"containerDefinitions": [
  {
    "name": "frontend",
    "image": "abc/frontend",
    "memory": 128,
    "hostname": "frontend",
    "essential": true                
  },
  {
    "name": "server",
    "image": "abc/"server",
    "memory": 128,
    "hostname": ""server",
    "essential": true        
  }
],
"links": ["frontend", "server"],
"memory": 128

}