diff --git a/app/models/ext_management_system.rb b/app/models/ext_management_system.rb
index 67ba767dfbd..8e2f72a5204 100644
--- a/app/models/ext_management_system.rb
+++ b/app/models/ext_management_system.rb
@@ -11,8 +11,12 @@ def self.with_tenant(tenant_id)
     where(:tenant_id => tenant.ancestor_ids + [tenant_id])
   end
 
+  def self.concrete_subclasses
+    leaf_subclasses | descendants.select { |d| d.try(:acts_as_sti_leaf_class?) }
+  end
+
   def self.types
-    leaf_subclasses.collect(&:ems_type)
+    concrete_subclasses.collect(&:ems_type)
   end
 
   def self.supported_types
@@ -20,7 +24,7 @@ def self.supported_types
   end
 
   def self.supported_subclasses
-    leaf_subclasses.select(&:permitted?)
+    concrete_subclasses.select(&:permitted?)
   end
 
   def self.permitted?
@@ -405,7 +409,7 @@ def self.model_name_from_emstype(emstype)
 
   def self.model_from_emstype(emstype)
     emstype = emstype.downcase
-    ExtManagementSystem.leaf_subclasses.detect { |k| k.ems_type == emstype }
+    ExtManagementSystem.concrete_subclasses.detect { |k| k.ems_type == emstype }
   end
 
   def self.short_token
diff --git a/app/models/miq_schedule_worker/runner.rb b/app/models/miq_schedule_worker/runner.rb
index d479a96fc7a..ecf7ac7d971 100644
--- a/app/models/miq_schedule_worker/runner.rb
+++ b/app/models/miq_schedule_worker/runner.rb
@@ -504,7 +504,7 @@ def do_work
 
   # @returns Hash<class, Integer> Hash of ems_class => refresh_interval
   def schedule_settings_for_ems_refresh
-    ExtManagementSystem.leaf_subclasses.each.with_object({}) do |klass, hash|
+    ExtManagementSystem.supported_subclasses.each.with_object({}) do |klass, hash|
       next unless klass.ems_type
       every = ::Settings.ems_refresh[klass.ems_type].try(:refresh_interval) || ::Settings.ems_refresh.refresh_interval
       every = every.respond_to?(:to_i_with_method) ? every.to_i_with_method : every.to_i
diff --git a/app/models/provider.rb b/app/models/provider.rb
index a753d433003..c3549afab27 100644
--- a/app/models/provider.rb
+++ b/app/models/provider.rb
@@ -25,14 +25,12 @@ class Provider < ApplicationRecord
 
   supports :refresh_ems
 
-  def self.leaf_subclasses
-    descendants.select { |d| d.subclasses.empty? }
+  def self.concrete_subclasses
+    leaf_subclasses | descendants.select { |d| d.try(:acts_as_sti_leaf_class?) }
   end
 
   def self.supported_subclasses
-    subclasses.flat_map do |s|
-      s.subclasses.empty? ? s : s.supported_subclasses
-    end
+    concrete_subclasses
   end
 
   def self.short_token
diff --git a/lib/acts_as_sti_leaf_class.rb b/lib/acts_as_sti_leaf_class.rb
new file mode 100644
index 00000000000..a1e00774ea2
--- /dev/null
+++ b/lib/acts_as_sti_leaf_class.rb
@@ -0,0 +1,14 @@
+module ActsAsStiLeafClass
+  extend ActiveSupport::Concern
+
+  module ClassMethods
+    def acts_as_sti_leaf_class?
+      true
+    end
+
+    private def type_condition(table = arel_table)
+      sti_column = table[inheritance_column]
+      predicate_builder.build(sti_column, [sti_name])
+    end
+  end
+end
diff --git a/spec/models/ext_management_system_spec.rb b/spec/models/ext_management_system_spec.rb
index a1beda76ce9..1cd040c8575 100644
--- a/spec/models/ext_management_system_spec.rb
+++ b/spec/models/ext_management_system_spec.rb
@@ -37,7 +37,7 @@
   end
 
   it ".model_name_from_emstype" do
-    described_class.leaf_subclasses.each do |klass|
+    described_class.concrete_subclasses.each do |klass|
       expect(described_class.model_name_from_emstype(klass.ems_type)).to eq(klass.name)
     end
     expect(described_class.model_name_from_emstype('foo')).to be_nil