diff --git a/aws/resource_aws_fsx_lustre_file_system.go b/aws/resource_aws_fsx_lustre_file_system.go
index 619b24dd1ba..f98d014cf8b 100644
--- a/aws/resource_aws_fsx_lustre_file_system.go
+++ b/aws/resource_aws_fsx_lustre_file_system.go
@@ -65,7 +65,9 @@ func resourceAwsFsxLustreFileSystem() *schema.Resource {
 				ValidateFunc: validation.IntBetween(1, 512000),
 			},
 			"network_interface_ids": {
-				Type:     schema.TypeSet,
+				// As explained in https://docs.aws.amazon.com/fsx/latest/LustreGuide/mounting-on-premises.html, the first
+				// network_interface_id is the primary one, so ordering matters. Use TypeList instead of TypeSet to preserve it.
+				Type:     schema.TypeList,
 				Computed: true,
 				Elem:     &schema.Schema{Type: schema.TypeString},
 			},
diff --git a/website/docs/r/fsx_lustre_file_system.html.markdown b/website/docs/r/fsx_lustre_file_system.html.markdown
index e8f7f83e8e1..0fe7f83c3aa 100644
--- a/website/docs/r/fsx_lustre_file_system.html.markdown
+++ b/website/docs/r/fsx_lustre_file_system.html.markdown
@@ -40,7 +40,7 @@ In addition to all arguments above, the following attributes are exported:
 * `arn` - Amazon Resource Name of the file system.
 * `dns_name` - DNS name for the file system, e.g. `fs-12345678.fsx.us-west-2.amazonaws.com`
 * `id` - Identifier of the file system, e.g. `fs-12345678`
-* `network_interface_ids` - Set of Elastic Network Interface identifiers from which the file system is accessible.
+* `network_interface_ids` - Set of Elastic Network Interface identifiers from which the file system is accessible. As explained in the [documentation](https://docs.aws.amazon.com/fsx/latest/LustreGuide/mounting-on-premises.html), the first network interface returned is the primary network interface.
 * `owner_id` - AWS account identifier that created the file system.
 * `vpc_id` - Identifier of the Virtual Private Cloud for the file system.