diff --git a/apollo-federation/src/operation/optimize.rs b/apollo-federation/src/operation/optimize.rs
index e9e897304f..bde0b6dfa9 100644
--- a/apollo-federation/src/operation/optimize.rs
+++ b/apollo-federation/src/operation/optimize.rs
@@ -1684,6 +1684,20 @@ impl FragmentGenerator {
                 SelectionValue::InlineFragment(mut candidate) => {
                     self.visit_selection_set(candidate.get_selection_set_mut())?;
 
+                    // XXX(@goto-bus-stop): This is temporary to support mismatch testing with JS!
+                    // JS federation does not consider fragments without a type condition.
+                    if candidate
+                        .get()
+                        .inline_fragment
+                        .type_condition_position
+                        .is_none()
+                    {
+                        new_selection_set.add_local_selection(&Selection::InlineFragment(
+                            Arc::clone(candidate.get()),
+                        ))?;
+                        continue;
+                    }
+
                     let directives = &candidate.get().inline_fragment.directives;
                     let skip_include = directives
                         .iter()
diff --git a/apollo-federation/tests/query_plan/build_query_plan_tests/fragment_autogeneration.rs b/apollo-federation/tests/query_plan/build_query_plan_tests/fragment_autogeneration.rs
index 876334fa5d..03b43c6245 100644
--- a/apollo-federation/tests/query_plan/build_query_plan_tests/fragment_autogeneration.rs
+++ b/apollo-federation/tests/query_plan/build_query_plan_tests/fragment_autogeneration.rs
@@ -177,6 +177,9 @@ fn it_handles_fragments_with_one_non_leaf_field() {
     );
 }
 
+/// XXX(@goto-bus-stop): this test is meant to check that fragments with @skip and @include *are*
+/// migrated. But we are currently matching JS behavior, where they are not. This test should be
+/// updated when we remove JS compatibility.
 #[test]
 fn it_migrates_skip_include() {
     let planner = planner!(
@@ -348,6 +351,50 @@ fn fragments_that_share_a_hash_but_are_not_identical_generate_their_own_fragment
     );
 }
 
+#[test]
+fn same_as_js_router798() {
+    let planner = planner!(
+        config = QueryPlannerConfig { generate_query_fragments: true, reuse_query_fragments: false, ..Default::default() },
+        Subgraph1: r#"
+            interface Interface { a: Int }
+            type Y implements Interface { a: Int b: Int }
+            type Z implements Interface { a: Int c: Int }
+
+            type Query {
+                interfaces(id: Int!): Interface
+            }
+        "#,
+    );
+    assert_plan!(
+        &planner,
+        r#"
+            query($var0: Boolean! = true) {
+              ... @skip(if: $var0) {
+                field0: interfaces(id: 0) {
+                  field1: __typename
+                }
+              }
+            }
+        "#,
+        @r###"
+    QueryPlan {
+      Skip(if: $var0) {
+        Fetch(service: "Subgraph1") {
+          {
+            ... {
+              field0: interfaces(id: 0) {
+                __typename
+                field1: __typename
+              }
+            }
+          }
+        },
+      },
+    }
+    "###
+    );
+}
+
 #[test]
 fn works_with_key_chains() {
     let planner = planner!(
diff --git a/apollo-federation/tests/query_plan/supergraphs/same_as_js_router798.graphql b/apollo-federation/tests/query_plan/supergraphs/same_as_js_router798.graphql
new file mode 100644
index 0000000000..6895c4bf96
--- /dev/null
+++ b/apollo-federation/tests/query_plan/supergraphs/same_as_js_router798.graphql
@@ -0,0 +1,73 @@
+# Composed from subgraphs with hash: ee7fce9eb672edf9b036a25bcae0b056ccf5f451
+schema
+  @link(url: "https://specs.apollo.dev/link/v1.0")
+  @link(url: "https://specs.apollo.dev/join/v0.4", for: EXECUTION)
+{
+  query: Query
+}
+
+directive @join__directive(graphs: [join__Graph!], name: String!, args: join__DirectiveArguments) repeatable on SCHEMA | OBJECT | INTERFACE | FIELD_DEFINITION
+
+directive @join__enumValue(graph: join__Graph!) repeatable on ENUM_VALUE
+
+directive @join__field(graph: join__Graph, requires: join__FieldSet, provides: join__FieldSet, type: String, external: Boolean, override: String, usedOverridden: Boolean, overrideLabel: String) repeatable on FIELD_DEFINITION | INPUT_FIELD_DEFINITION
+
+directive @join__graph(name: String!, url: String!) on ENUM_VALUE
+
+directive @join__implements(graph: join__Graph!, interface: String!) repeatable on OBJECT | INTERFACE
+
+directive @join__type(graph: join__Graph!, key: join__FieldSet, extension: Boolean! = false, resolvable: Boolean! = true, isInterfaceObject: Boolean! = false) repeatable on OBJECT | INTERFACE | UNION | ENUM | INPUT_OBJECT | SCALAR
+
+directive @join__unionMember(graph: join__Graph!, member: String!) repeatable on UNION
+
+directive @link(url: String, as: String, for: link__Purpose, import: [link__Import]) repeatable on SCHEMA
+
+interface Interface
+  @join__type(graph: SUBGRAPH1)
+{
+  a: Int
+}
+
+scalar join__DirectiveArguments
+
+scalar join__FieldSet
+
+enum join__Graph {
+  SUBGRAPH1 @join__graph(name: "Subgraph1", url: "none")
+}
+
+scalar link__Import
+
+enum link__Purpose {
+  """
+  `SECURITY` features provide metadata necessary to securely resolve fields.
+  """
+  SECURITY
+
+  """
+  `EXECUTION` features provide metadata necessary for operation execution.
+  """
+  EXECUTION
+}
+
+type Query
+  @join__type(graph: SUBGRAPH1)
+{
+  interfaces(id: Int!): Interface
+}
+
+type Y implements Interface
+  @join__implements(graph: SUBGRAPH1, interface: "Interface")
+  @join__type(graph: SUBGRAPH1)
+{
+  a: Int
+  b: Int
+}
+
+type Z implements Interface
+  @join__implements(graph: SUBGRAPH1, interface: "Interface")
+  @join__type(graph: SUBGRAPH1)
+{
+  a: Int
+  c: Int
+}