diff --git a/builtin/providers/aws/resource_aws_config_config_rule.go b/builtin/providers/aws/resource_aws_config_config_rule.go
index e4f2e5c6b..a5c86c334 100644
--- a/builtin/providers/aws/resource_aws_config_config_rule.go
+++ b/builtin/providers/aws/resource_aws_config_config_rule.go
@@ -110,6 +110,7 @@ func resourceAwsConfigConfigRule() *schema.Resource {
 									"event_source": {
 										Type:     schema.TypeString,
 										Optional: true,
+										Default:  "aws.config",
 									},
 									"maximum_execution_frequency": {
 										Type:         schema.TypeString,
diff --git a/website/source/docs/providers/aws/r/config_config_rule.html.markdown b/website/source/docs/providers/aws/r/config_config_rule.html.markdown
index 552154744..dae253fe9 100644
--- a/website/source/docs/providers/aws/r/config_config_rule.html.markdown
+++ b/website/source/docs/providers/aws/r/config_config_rule.html.markdown
@@ -108,7 +108,7 @@ Provides the rule owner (AWS or customer), the rule identifier, and the notifica
 	For custom rules, the identifier is the ARN of the rule's AWS Lambda function, such as `arn:aws:lambda:us-east-1:123456789012:function:custom_rule_name`.
 * `source_detail` - (Optional) Provides the source and type of the event that causes AWS Config to evaluate your AWS resources. Only valid if `owner` is `CUSTOM_LAMBDA`.
 	* `event_source` - (Optional) The source of the event, such as an AWS service, that triggers AWS Config
-		to evaluate your AWS resources. The only valid value is `aws.config`.
+		to evaluate your AWS resources. This defaults to `aws.config` and is the only valid value.
 	* `maximum_execution_frequency` - (Optional) The frequency that you want AWS Config to run evaluations for a rule that
 		is triggered periodically. If specified, requires `message_type` to be `ScheduledNotification`.
 	* `message_type` - (Optional) The type of notification that triggers AWS Config to run an evaluation for a rule. You can specify the following notification types: