Elastic MapReduce with boto - InstanceProfile is required for creating cluster

Im trying to do a elastic mapreduce job with code below, but when I try this I get an error: InstanceProfile is required for creating cluster

Someone knows why Im getting this error?

def createmrjob(dict):  
    emr = boto.emr.connect_to_region('us-east-1')

    print ""
    print "Conected to Elastic MapReduce."

    print "Creating Streaming step"

    bucket = dict['bucket']
    print bucket
    step = StreamingStep(name='Test',
    mapper=dict['mapper'],
    reducer=dict['reducer'],
    input=msg['datafile'],
    output='s3n://'+bucket+'/uploadedfiles/')

    print "Creating job flow"
    jobid = emr.run_jobflow(name="Data Processing", 
    log_uri="s3://"+bucket+"/uploadedfiles/erm_logs/",
    steps=[step],
    num_instances = 1,
    )

createmrjob(msg)