diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs
index 841f602d985cd..3b4482146d4f1 100644
--- a/compiler/rustc_ty_utils/src/opaque_types.rs
+++ b/compiler/rustc_ty_utils/src/opaque_types.rs
@@ -321,7 +321,10 @@ fn opaque_types_defined_by<'tcx>(
             collector.collect_taits_declared_in_body();
         }
         // Closures and coroutines are type checked with their parent
-        DefKind::Closure | DefKind::InlineConst => {
+        // Note that we also support `SyntheticCoroutineBody` since we create
+        // a MIR body for the def kind, and some MIR passes (like promotion)
+        // may require doing analysis using its typing env.
+        DefKind::Closure | DefKind::InlineConst | DefKind::SyntheticCoroutineBody => {
             collector.opaques.extend(tcx.opaque_types_defined_by(tcx.local_parent(item)));
         }
         DefKind::AssocTy | DefKind::TyAlias | DefKind::GlobalAsm => {}
@@ -343,8 +346,7 @@ fn opaque_types_defined_by<'tcx>(
         | DefKind::ForeignMod
         | DefKind::Field
         | DefKind::LifetimeParam
-        | DefKind::Impl { .. }
-        | DefKind::SyntheticCoroutineBody => {
+        | DefKind::Impl { .. } => {
             span_bug!(
                 tcx.def_span(item),
                 "`opaque_types_defined_by` not defined for {} `{item:?}`",
diff --git a/tests/ui/async-await/async-closures/promote-in-body.rs b/tests/ui/async-await/async-closures/promote-in-body.rs
new file mode 100644
index 0000000000000..ea95d680987e0
--- /dev/null
+++ b/tests/ui/async-await/async-closures/promote-in-body.rs
@@ -0,0 +1,13 @@
+//@ build-pass
+//@ compile-flags: --crate-type=lib
+//@ edition: 2024
+
+union U {
+    f: i32,
+}
+
+fn foo() {
+    async || {
+        &U { f: 1 }
+    };
+}