diff --git a/internal/services/authorization/role_assignment_resource.go b/internal/services/authorization/role_assignment_resource.go
index 727737b0b688..07ca1ba55d6f 100644
--- a/internal/services/authorization/role_assignment_resource.go
+++ b/internal/services/authorization/role_assignment_resource.go
@@ -101,7 +101,14 @@ func resourceArmRoleAssignment() *pluginsdk.Resource {
 
 			"principal_type": {
 				Type:     pluginsdk.TypeString,
+				Optional: true,
 				Computed: true,
+				ForceNew: true,
+				ValidateFunc: validation.StringInSlice([]string{
+					"User",
+					"Group",
+					"ServicePrincipal",
+				}, false),
 			},
 
 			"skip_service_principal_aad_check": {
@@ -234,6 +241,11 @@ func resourceArmRoleAssignmentCreate(d *pluginsdk.ResourceData, meta interface{}
 		properties.RoleAssignmentProperties.PrincipalType = authorization.ServicePrincipal
 	}
 
+	principalType := d.Get("principal_type").(string)
+	if principalType != "" {
+		properties.RoleAssignmentProperties.PrincipalType = authorization.PrincipalType(principalType)
+	}
+
 	if err := pluginsdk.Retry(d.Timeout(pluginsdk.TimeoutCreate), retryRoleAssignmentsClient(d, scope, name, properties, meta, tenantId)); err != nil {
 		return err
 	}
diff --git a/website/docs/r/role_assignment.html.markdown b/website/docs/r/role_assignment.html.markdown
index 1a4afa55f1ce..f81eb0417fac 100644
--- a/website/docs/r/role_assignment.html.markdown
+++ b/website/docs/r/role_assignment.html.markdown
@@ -143,6 +143,8 @@ The following arguments are supported:
 
 ~> **NOTE:** The Principal ID is also known as the Object ID (ie not the "Application ID" for applications).
 
+* `principal_type` - (Optional) The type of the `principal_id`. Possible values are `User`, `Group`, or `ServicePrincpal`.
+
 * `condition` - (Optional) The condition that limits the resources that the role can be assigned to. Changing this forces a new resource to be created.
 
 * `condition_version` - (Optional) The version of the condition. Possible values are `1.0` or `2.0`. Changing this forces a new resource to be created.
@@ -152,7 +154,7 @@ The following arguments are supported:
 ~> **NOTE:** this field is only used in cross tenant scenario.
 
 * `description` - (Optional) The description for this Role Assignment. Changing this forces a new resource to be created.
-  
+
 * `skip_service_principal_aad_check` - (Optional) If the `principal_id` is a newly provisioned `Service Principal` set this value to `true` to skip the `Azure Active Directory` check which may fail due to replication lag. This argument is only valid if the `principal_id` is a `Service Principal` identity. Defaults to `false`.
 
 ~> **NOTE:** If it is not a `Service Principal` identity it will cause the role assignment to fail.
@@ -163,8 +165,6 @@ In addition to the Arguments listed above - the following Attributes are exporte
 
 * `id` - The Role Assignment ID.
 
-* `principal_type` - The type of the `principal_id`, e.g. User, Group, Service Principal, Application, etc.
-
 ## Timeouts
 
 The `timeouts` block allows you to specify [timeouts](https://www.terraform.io/language/resources/syntax#operation-timeouts) for certain actions: