diff --git a/compiler/rustc_smir/src/rustc_smir/context.rs b/compiler/rustc_smir/src/rustc_smir/context.rs
index 93d49038fc1..6dc569b8f6a 100644
--- a/compiler/rustc_smir/src/rustc_smir/context.rs
+++ b/compiler/rustc_smir/src/rustc_smir/context.rs
@@ -187,9 +187,9 @@ impl<'tcx> Context for TablesWrapper<'tcx> {
         new_item_kind(tables.tcx.def_kind(tables[item.0]))
     }
 
-    fn is_foreign_item(&self, item: CrateItem) -> bool {
+    fn is_foreign_item(&self, item: DefId) -> bool {
         let tables = self.0.borrow();
-        tables.tcx.is_foreign_item(tables[item.0])
+        tables.tcx.is_foreign_item(tables[item])
     }
 
     fn adt_kind(&self, def: AdtDef) -> AdtKind {
diff --git a/compiler/stable_mir/src/compiler_interface.rs b/compiler/stable_mir/src/compiler_interface.rs
index d8a3d4eda4b..5c91ec15455 100644
--- a/compiler/stable_mir/src/compiler_interface.rs
+++ b/compiler/stable_mir/src/compiler_interface.rs
@@ -60,7 +60,7 @@ pub trait Context {
     fn item_kind(&self, item: CrateItem) -> ItemKind;
 
     /// Returns whether this is a foreign item.
-    fn is_foreign_item(&self, item: CrateItem) -> bool;
+    fn is_foreign_item(&self, item: DefId) -> bool;
 
     /// Returns the kind of a given algebraic data type
     fn adt_kind(&self, def: AdtDef) -> AdtKind;
diff --git a/compiler/stable_mir/src/lib.rs b/compiler/stable_mir/src/lib.rs
index 2099c485c6f..1e7495009d8 100644
--- a/compiler/stable_mir/src/lib.rs
+++ b/compiler/stable_mir/src/lib.rs
@@ -120,7 +120,7 @@ impl CrateItem {
     }
 
     pub fn is_foreign_item(&self) -> bool {
-        with(|cx| cx.is_foreign_item(*self))
+        with(|cx| cx.is_foreign_item(self.0))
     }
 
     pub fn dump<W: io::Write>(&self, w: &mut W) -> io::Result<()> {
diff --git a/compiler/stable_mir/src/mir/mono.rs b/compiler/stable_mir/src/mir/mono.rs
index 10270c82e63..11b849868e0 100644
--- a/compiler/stable_mir/src/mir/mono.rs
+++ b/compiler/stable_mir/src/mir/mono.rs
@@ -39,9 +39,16 @@ impl Instance {
         with(|context| context.instance_body(self.def))
     }
 
+    /// Check whether this instance has a body available.
+    ///
+    /// This call is much cheaper than `instance.body().is_some()`, since it doesn't try to build
+    /// the StableMIR body.
+    pub fn has_body(&self) -> bool {
+        with(|cx| cx.has_body(self.def.def_id()))
+    }
+
     pub fn is_foreign_item(&self) -> bool {
-        let item = CrateItem::try_from(*self);
-        item.as_ref().is_ok_and(CrateItem::is_foreign_item)
+        with(|cx| cx.is_foreign_item(self.def.def_id()))
     }
 
     /// Get the instance type with generic substitutions applied and lifetimes erased.
diff --git a/tests/ui-fulldeps/stable-mir/check_instance.rs b/tests/ui-fulldeps/stable-mir/check_instance.rs
index 976dfee774b..5cb07eabf41 100644
--- a/tests/ui-fulldeps/stable-mir/check_instance.rs
+++ b/tests/ui-fulldeps/stable-mir/check_instance.rs
@@ -64,8 +64,12 @@ fn test_body(body: mir::Body) {
                 let RigidTy::FnDef(def, args) = ty else { unreachable!() };
                 let instance = Instance::resolve(def, &args).unwrap();
                 let mangled_name = instance.mangled_name();
-                let body = instance.body();
-                assert!(body.is_some() || mangled_name == "setpwent", "Failed: {func:?}");
+                assert!(instance.has_body() || (mangled_name == "setpwent"), "Failed: {func:?}");
+                assert!(instance.has_body() ^ instance.is_foreign_item());
+                if instance.has_body() {
+                    let body = instance.body().unwrap();
+                    assert!(!body.locals().is_empty(), "Body must at least have a return local");
+                }
             }
             Goto { .. } | Assert { .. } | SwitchInt { .. } | Return | Drop { .. } => {
                 /* Do nothing */