diff --git a/legend-engine-core/legend-engine-core-pure/legend-engine-pure-code-compiled-core/src/main/resources/core/pure/binding/executionPlan/executionPlan_generation.pure b/legend-engine-core/legend-engine-core-pure/legend-engine-pure-code-compiled-core/src/main/resources/core/pure/binding/executionPlan/executionPlan_generation.pure
index daba5b5336f..66bb88459d3 100644
--- a/legend-engine-core/legend-engine-core-pure/legend-engine-pure-code-compiled-core/src/main/resources/core/pure/binding/executionPlan/executionPlan_generation.pure
+++ b/legend-engine-core/legend-engine-core-pure/legend-engine-pure-code-compiled-core/src/main/resources/core/pure/binding/executionPlan/executionPlan_generation.pure
@@ -252,7 +252,12 @@ function meta::external::format::shared::executionPlan::extractPackageableElemen
                                                                  )->concatenate($p.subType),
                                   s:SubTypeGraphFetchTree[1]   | $s.subTypeClass
                                 ])->cast(@PackageableElement);
-  $classesFromTree->concatenate($tree.subTrees->map(s | $s->extractPackageableElementFromTree()))->concatenate($tree.subTypeTrees->map(s | $s->extractPackageableElementFromTree()));
+  let specializations = $classesFromTree->filter(c | $c->instanceOf(Class))->map(c | $c->cast(@Class<Any>)->meta::pure::functions::meta::findAllSpecializations())->filter(x | $x->elementToPath() != Any->elementToPath());
+  let generalizations = $classesFromTree->filter(c | $c->instanceOf(Class))->map(c | $c->cast(@Class<Any>)->meta::pure::functions::meta::getAllTypeGeneralisations())->filter(x | $x->elementToPath() != Any->elementToPath())
+                                        ->filter(x | $x->instanceOf(PackageableElement))->cast(@PackageableElement);
+  let currentLevelClasses = $classesFromTree->concatenate($specializations)->concatenate($generalizations)->removeDuplicates({a, b | $a->elementToPath() == $b->elementToPath()});
+
+  $currentLevelClasses->concatenate($tree.subTrees->map(s | $s->extractPackageableElementFromTree()))->concatenate($tree.subTypeTrees->map(s | $s->extractPackageableElementFromTree()));
 }
 
 function <<access.private>> meta::external::format::shared::executionPlan::getFunctionProcessor(f:SimpleFunctionExpression[1], extensions:meta::pure::extension::Extension[*]):meta::pure::metamodel::function::Function<{FunctionExpression[1], ExternalFormatPlanGenerationState[1], Extension[*], DebugContext[1] -> ExecutionNode[1]}>[1]
diff --git a/legend-engine-xts-json/legend-engine-xt-json-pure/src/main/resources/core_external_format_json/executionPlan/tests/simple.pure b/legend-engine-xts-json/legend-engine-xt-json-pure/src/main/resources/core_external_format_json/executionPlan/tests/simple.pure
index c62d46f16e0..4e33245688e 100644
--- a/legend-engine-xts-json/legend-engine-xt-json-pure/src/main/resources/core_external_format_json/executionPlan/tests/simple.pure
+++ b/legend-engine-xts-json/legend-engine-xt-json-pure/src/main/resources/core_external_format_json/executionPlan/tests/simple.pure
@@ -147,6 +147,15 @@ function <<meta::pure::profiles::test.Test, meta::pure::profiles::test.AlloyOnly
   assertEquals('{"defects":[],"source":{"number":1,"record":"{\\\"firstName\\\":\\\"John\\\",\\\"lastName\\\":\\\"Doe\\\",\\\"firm\\\":{\\\"legalName\\\":\\\"Firm A\\\"}}"},"value":{"firstName":"John","lastName":"Doe"}}', $result);
 }
 
+function <<meta::pure::profiles::test.Test, meta::pure::profiles::test.AlloyOnly>> meta::external::format::json::executionPlan::test::simple::testSimpleJsonQueryWithChildSubType(): Boolean[1]
+{
+  let query   = {data:String[1]| Target.all()->graphFetch(#{Target{targetProductId}}#)->serialize(#{Target{targetProductId}}#)->from(M2MMappingWithChild, Source->getRuntimeWithModelQueryConnection('application/json', $data))};
+
+  let result  = meta::external::format::json::executionPlan::test::executeJsonSchemaBindingQuery($query, pair('data', '{"@type": "Source", "child": {"@type": "ProductExtended", "productId": "123"}}'));
+
+  assertEquals('{"builder":{"_type":"json"},"values":{"targetProductId":"123"}}', $result);
+}
+
 function <<meta::pure::profiles::test.Test, meta::pure::profiles::test.AlloyOnly>> meta::external::format::json::executionPlan::test::simple::testM2MChainingWithJson(): Boolean[1]
 {
   let binding = getTestBinding();
@@ -357,6 +366,20 @@ Class meta::external::format::json::executionPlan::test::simple::Product
   description: String[1];
 }
 
+Class meta::external::format::json::executionPlan::test::simple::ProductExtended extends meta::external::format::json::executionPlan::test::simple::Product
+{
+}
+
+Class meta::external::format::json::executionPlan::test::simple::Target
+{
+  targetProductId: String[1];
+}
+
+Class meta::external::format::json::executionPlan::test::simple::Source
+{
+  child: meta::external::format::json::executionPlan::test::simple::Product[1];
+}
+
 Class meta::external::format::json::executionPlan::test::simple::Synonym
 {
   name: String[1];
@@ -507,6 +530,15 @@ Mapping meta::external::format::json::executionPlan::test::simple::M2MMapping2
   }
 )
 
+Mapping meta::external::format::json::executionPlan::test::simple::M2MMappingWithChild
+(
+  meta::external::format::json::executionPlan::test::simple::Target: Pure
+  {
+    ~src meta::external::format::json::executionPlan::test::simple::Source
+    targetProductId: $src.child.productId
+  }
+)
+
 Mapping meta::external::format::json::executionPlan::test::simple::M2MCrossStoreMapping
 (
   meta::external::format::json::executionPlan::test::simple::Trade[trade_set]: Pure