diff --git a/aws-py-assume-role/assume-role/__main__.py b/aws-py-assume-role/assume-role/__main__.py
index ba749343d..1390ccf2f 100644
--- a/aws-py-assume-role/assume-role/__main__.py
+++ b/aws-py-assume-role/assume-role/__main__.py
@@ -24,7 +24,7 @@
         region=aws_config.require("region"),
         assume_roles=[
             {
-                "role_arn": role_to_assume_arn,
+                "roleArn": role_to_assume_arn,
                 # session name can contain only the following special characters =,.@-
                 # if any other special character is used, an error stating that the role
                 # cannot be assumed will be returned