diff --git a/src/tools/rust-analyzer/crates/hir/src/semantics.rs b/src/tools/rust-analyzer/crates/hir/src/semantics.rs
index e55b693ef018..98f5739600f3 100644
--- a/src/tools/rust-analyzer/crates/hir/src/semantics.rs
+++ b/src/tools/rust-analyzer/crates/hir/src/semantics.rs
@@ -641,11 +641,14 @@ impl<'db> SemanticsImpl<'db> {
         })
     }
 
-    pub fn expand_derive_macro(&self, attr: &ast::Attr) -> Option<Vec<ExpandResult<SyntaxNode>>> {
+    pub fn expand_derive_macro(
+        &self,
+        attr: &ast::Attr,
+    ) -> Option<Vec<Option<ExpandResult<SyntaxNode>>>> {
         let res: Vec<_> = self
             .derive_macro_calls(attr)?
             .into_iter()
-            .flat_map(|call| {
+            .map(|call| {
                 let file_id = call?.left()?;
                 let ExpandResult { value, err } = self.db.parse_macro_expansion(file_id);
                 let root_node = value.0.syntax_node();
diff --git a/src/tools/rust-analyzer/crates/ide/src/expand_macro.rs b/src/tools/rust-analyzer/crates/ide/src/expand_macro.rs
index ba8b3aa9cafe..44285d9315af 100644
--- a/src/tools/rust-analyzer/crates/ide/src/expand_macro.rs
+++ b/src/tools/rust-analyzer/crates/ide/src/expand_macro.rs
@@ -63,7 +63,7 @@ pub(crate) fn expand_macro(db: &RootDatabase, position: FilePosition) -> Option<
             .take_while(|it| it != &token)
             .filter(|it| it.kind() == T![,])
             .count();
-        let ExpandResult { err, value: expansion } = expansions.get(idx)?.clone();
+        let ExpandResult { err, value: expansion } = expansions.get(idx)?.clone()?;
         let expansion_file_id = sema.hir_file_for(&expansion).macro_file()?;
         let expansion_span_map = db.expansion_span_map(expansion_file_id);
         let mut expansion = format(
@@ -848,4 +848,19 @@ struct S {
                 u32"#]],
         );
     }
+
+    #[test]
+    fn regression_21489() {
+        check(
+            r#"
+//- proc_macros: derive_identity
+//- minicore: derive, fmt
+#[derive(Debug, proc_macros::DeriveIdentity$0)]
+struct Foo;
+        "#,
+            expect![[r#"
+                proc_macros::DeriveIdentity
+                struct Foo;"#]],
+        );
+    }
 }