diff --git a/frappe/custom/doctype/customize_form/customize_form.py b/frappe/custom/doctype/customize_form/customize_form.py
index a7b26f18c9..6c8096de96 100644
--- a/frappe/custom/doctype/customize_form/customize_form.py
+++ b/frappe/custom/doctype/customize_form/customize_form.py
@@ -89,6 +89,9 @@ class CustomizeForm(Document):
 		if self.doc_type in core_doctypes_list:
 			return frappe.msgprint(_("Core DocTypes cannot be customized."))
 
+		if meta.issingle:
+			return frappe.msgprint(_("Single DocTypes cannot be customized."))
+
 		if meta.custom:
 			return frappe.msgprint(_("Only standard DocTypes are allowed to be customized from Customize Form."))
 
diff --git a/frappe/public/js/frappe/form/toolbar.js b/frappe/public/js/frappe/form/toolbar.js
index 99d913f1cd..b4c7667afc 100644
--- a/frappe/public/js/frappe/form/toolbar.js
+++ b/frappe/public/js/frappe/form/toolbar.js
@@ -167,7 +167,7 @@ frappe.ui.form.Toolbar = Class.extend({
 				me.frm.savetrash();}, true);
 		}
 
-		if(frappe.user_roles.includes("System Manager")) {
+		if(frappe.user_roles.includes("System Manager") && me.frm.meta.issingle === 0) {
 			this.page.add_menu_item(__("Customize"), function() {
 				frappe.set_route("Form", "Customize Form", {
 					doc_type: me.frm.doctype