diff --git a/thrift/annotation/rust.thrift b/thrift/annotation/rust.thrift
index 5d4e7eacbae..e22294010d7 100644
--- a/thrift/annotation/rust.thrift
+++ b/thrift/annotation/rust.thrift
@@ -80,6 +80,7 @@ struct Exhaustive {
 
 @scope.Struct
 @scope.Typedef
+@scope.Union
 struct Ord {
 // # `rust.Ord`
 //
diff --git a/thrift/compiler/test/fixtures/adapter/out/hack/gen-hack/rust_types.php b/thrift/compiler/test/fixtures/adapter/out/hack/gen-hack/rust_types.php
index d7a26108054..4f9b8611e17 100644
--- a/thrift/compiler/test/fixtures/adapter/out/hack/gen-hack/rust_types.php
+++ b/thrift/compiler/test/fixtures/adapter/out/hack/gen-hack/rust_types.php
@@ -616,6 +616,10 @@ public static function getAllStructuredAnnotations()[write_props]: \TStructAnnot
           shape(
           )
         ),
+        '\facebook\thrift\annotation\Union' => \facebook\thrift\annotation\Union::fromShape(
+          shape(
+          )
+        ),
       ],
       'fields' => dict[
       ],
diff --git a/thrift/compiler/test/fixtures/adapter/out/json/gen-json/rust.json b/thrift/compiler/test/fixtures/adapter/out/json/gen-json/rust.json
index fd6fcc7f910..f96fc45855c 100644
--- a/thrift/compiler/test/fixtures/adapter/out/json/gen-json/rust.json
+++ b/thrift/compiler/test/fixtures/adapter/out/json/gen-json/rust.json
@@ -142,13 +142,13 @@
           "column" : 1
         },
         "end" : {
-          "line" : 87,
+          "line" : 88,
           "column" : 2
         }
       }
     },
     "NewType" : {
-      "lineno" : 89,
+      "lineno" : 90,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -156,17 +156,17 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 89,
+          "line" : 90,
           "column" : 1
         },
         "end" : {
-          "line" : 108,
+          "line" : 109,
           "column" : 2
         }
       }
     },
     "Type" : {
-      "lineno" : 110,
+      "lineno" : 111,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -176,11 +176,11 @@
           "required" : true,
           "source_range" : {
             "begin" : {
-              "line" : 264,
+              "line" : 265,
               "column" : 3
             },
             "end" : {
-              "line" : 264,
+              "line" : 265,
               "column" : 18
             }
           }
@@ -188,17 +188,17 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 110,
+          "line" : 111,
           "column" : 1
         },
         "end" : {
-          "line" : 265,
+          "line" : 266,
           "column" : 2
         }
       }
     },
     "Serde" : {
-      "lineno" : 271,
+      "lineno" : 272,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -208,11 +208,11 @@
           "required" : true,
           "source_range" : {
             "begin" : {
-              "line" : 273,
+              "line" : 274,
               "column" : 3
             },
             "end" : {
-              "line" : 273,
+              "line" : 274,
               "column" : 19
             }
           }
@@ -220,17 +220,17 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 271,
+          "line" : 272,
           "column" : 1
         },
         "end" : {
-          "line" : 274,
+          "line" : 275,
           "column" : 2
         }
       }
     },
     "Mod" : {
-      "lineno" : 280,
+      "lineno" : 281,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -240,11 +240,11 @@
           "required" : true,
           "source_range" : {
             "begin" : {
-              "line" : 282,
+              "line" : 283,
               "column" : 3
             },
             "end" : {
-              "line" : 282,
+              "line" : 283,
               "column" : 18
             }
           }
@@ -252,17 +252,17 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 280,
+          "line" : 281,
           "column" : 1
         },
         "end" : {
-          "line" : 283,
+          "line" : 284,
           "column" : 2
         }
       }
     },
     "Adapter" : {
-      "lineno" : 285,
+      "lineno" : 286,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -272,11 +272,11 @@
           "required" : true,
           "source_range" : {
             "begin" : {
-              "line" : 330,
+              "line" : 331,
               "column" : 3
             },
             "end" : {
-              "line" : 330,
+              "line" : 331,
               "column" : 18
             }
           }
@@ -284,17 +284,17 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 285,
+          "line" : 286,
           "column" : 1
         },
         "end" : {
-          "line" : 331,
+          "line" : 332,
           "column" : 2
         }
       }
     },
     "Derive" : {
-      "lineno" : 333,
+      "lineno" : 334,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -304,11 +304,11 @@
           "required" : true,
           "source_range" : {
             "begin" : {
-              "line" : 356,
+              "line" : 357,
               "column" : 3
             },
             "end" : {
-              "line" : 356,
+              "line" : 357,
               "column" : 27
             }
           }
@@ -316,17 +316,17 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 333,
+          "line" : 334,
           "column" : 1
         },
         "end" : {
-          "line" : 357,
+          "line" : 358,
           "column" : 2
         }
       }
     },
     "ServiceExn" : {
-      "lineno" : 359,
+      "lineno" : 360,
       "is_exception" : false,
       "is_union" : false,
       "fields" : {
@@ -336,11 +336,11 @@
           "required" : true,
           "source_range" : {
             "begin" : {
-              "line" : 410,
+              "line" : 411,
               "column" : 3
             },
             "end" : {
-              "line" : 410,
+              "line" : 411,
               "column" : 37
             }
           }
@@ -348,11 +348,11 @@
       },
       "source_range" : {
         "begin" : {
-          "line" : 359,
+          "line" : 360,
           "column" : 1
         },
         "end" : {
-          "line" : 411,
+          "line" : 412,
           "column" : 2
         }
       }
diff --git a/thrift/compiler/test/fixtures/hack_service/out/hack_module2_with_patch/gen-hack/rust_types.php b/thrift/compiler/test/fixtures/hack_service/out/hack_module2_with_patch/gen-hack/rust_types.php
index 564354820d3..a76c086b438 100644
--- a/thrift/compiler/test/fixtures/hack_service/out/hack_module2_with_patch/gen-hack/rust_types.php
+++ b/thrift/compiler/test/fixtures/hack_service/out/hack_module2_with_patch/gen-hack/rust_types.php
@@ -488,6 +488,10 @@ public static function getAllStructuredAnnotations()[write_props]: \TStructAnnot
           shape(
           )
         ),
+        '\facebook\thrift\annotation\Union' => \facebook\thrift\annotation\Union::fromShape(
+          shape(
+          )
+        ),
       ],
       'fields' => dict[
       ],
diff --git a/thrift/compiler/test/fixtures/rust-annotations/out/rust/gen-rust/types.rs b/thrift/compiler/test/fixtures/rust-annotations/out/rust/gen-rust/types.rs
index 9ecd1230293..0717a19d2a1 100644
--- a/thrift/compiler/test/fixtures/rust-annotations/out/rust/gen-rust/types.rs
+++ b/thrift/compiler/test/fixtures/rust-annotations/out/rust/gen-rust/types.rs
@@ -170,6 +170,7 @@ pub struct U10 {
 pub enum U11 {
     string(::std::string::String),
     integer(::std::primitive::i32),
+    btreeset(::std::collections::BTreeSet<crate::types::U11>),
     UnknownField(::std::primitive::i32),
 }
 
@@ -2110,6 +2111,11 @@ where
                 ::fbthrift::Serialize::write(inner, p);
                 p.write_field_end();
             }
+            Self::btreeset(inner) => {
+                p.write_field_begin("btreeset", ::fbthrift::TType::Set, 3);
+                ::fbthrift::Serialize::write(inner, p);
+                p.write_field_end();
+            }
             Self::UnknownField(_) => {}
         }
         p.write_field_stop();
@@ -2124,6 +2130,7 @@ where
     #[inline]
     fn read(p: &mut P) -> ::anyhow::Result<Self> {
         static FIELDS: &[::fbthrift::Field] = &[
+            ::fbthrift::Field::new("btreeset", ::fbthrift::TType::Set, 3),
             ::fbthrift::Field::new("integer", ::fbthrift::TType::I32, 2),
             ::fbthrift::Field::new("str", ::fbthrift::TType::String, 1),
         ];
@@ -2142,6 +2149,10 @@ where
                     once = true;
                     alt = ::std::option::Option::Some(Self::integer(::fbthrift::Deserialize::read(p)?));
                 }
+                (::fbthrift::TType::Set, 3, false) => {
+                    once = true;
+                    alt = ::std::option::Option::Some(Self::btreeset(::fbthrift::Deserialize::read(p)?));
+                }
                 (fty, _, false) => p.skip(fty)?,
                 (badty, badid, true) => return ::std::result::Result::Err(::std::convert::From::from(::fbthrift::ProtocolError::UnwantedExtraUnionField(
                     "T11".to_string(),
@@ -2162,6 +2173,7 @@ impl U11 {
         match self {
             Self::string(_) => ::std::option::Option::Some(("string", "str")),
             Self::integer(_) => ::std::option::Option::Some(("integer", "integer")),
+            Self::btreeset(_) => ::std::option::Option::Some(("btreeset", "btreeset")),
             Self::UnknownField(_) => ::std::option::Option::None,
         }
     }
@@ -2182,6 +2194,15 @@ impl ::fbthrift::metadata::ThriftAnnotations for U11 {
             return r.take();
         }
 
+        if type_id == ::std::any::TypeId::of::<rust__types::Ord>() {
+            let mut tmp = ::std::option::Option::Some(rust__types::Ord {
+                ..::std::default::Default::default()
+            });
+            let r: &mut dyn ::std::any::Any = &mut tmp;
+            let r: &mut ::std::option::Option<T> = r.downcast_mut().unwrap();
+            return r.take();
+        }
+
         ::std::option::Option::None
     }
 
@@ -2205,6 +2226,8 @@ impl ::fbthrift::metadata::ThriftAnnotations for U11 {
             },
             2 => {
             },
+            3 => {
+            },
             _ => {}
         }
 
diff --git a/thrift/compiler/test/fixtures/rust-annotations/src/module.thrift b/thrift/compiler/test/fixtures/rust-annotations/src/module.thrift
index f8c5f9fc9d8..4f8b5ad7dd6 100644
--- a/thrift/compiler/test/fixtures/rust-annotations/src/module.thrift
+++ b/thrift/compiler/test/fixtures/rust-annotations/src/module.thrift
@@ -136,10 +136,12 @@ struct T10 {
 typedef i64 t_t1
 
 @rust.Name{name = "U11"}
+@rust.Ord
 union T11 {
   @rust.Name{name = "string"}
   1: string str;
   2: i32 integer;
+  3: set<T11> btreeset;
 }
 
 // --