diff --git a/crates/formula/src/adjust.rs b/crates/formula/src/adjust.rs
index ae082a6..7feb904 100644
--- a/crates/formula/src/adjust.rs
+++ b/crates/formula/src/adjust.rs
@@ -218,6 +218,13 @@ pub fn rename_sheet(e: Expr, old: &str, new: &str) -> Expr {
             }
             Expr::Ref(r)
         }
+        // Sheet-qualified defined name `Old!MyName` is stored as one string.
+        Expr::Name(n) => match n.split_at_checked(old.len()) {
+            Some((head, rest)) if head.eq_ignore_ascii_case(old) && rest.starts_with('!') => {
+                Expr::Name(format!("{}{rest}", crate::printer::quote_sheet(new)))
+            }
+            _ => Expr::Name(n),
+        },
         other => other,
     })
 }
diff --git a/crates/formula/src/tests.rs b/crates/formula/src/tests.rs
index ee89070..3aca4a5 100644
--- a/crates/formula/src/tests.rs
+++ b/crates/formula/src/tests.rs
@@ -163,6 +163,14 @@ fn moves_and_renames() {
     assert_eq!(print(&rename_sheet(e, "Old", "New Name")), "'New Name'!A1+'New Name'!B2");
 }
 
+#[test]
+fn rename_sheet_updates_qualified_names() {
+    let e = parse("Data!MyName+MyName+Other!MyName").unwrap();
+    assert_eq!(print(&rename_sheet(e, "data", "Numbers")), "Numbers!MyName+MyName+Other!MyName");
+    let e = parse("Data!MyName").unwrap();
+    assert_eq!(print(&rename_sheet(e, "Data", "New Name")), "'New Name'!MyName");
+}
+
 #[test]
 fn r1c1() {
     let e = parse("A1+$B$2+SUM(C:C)").unwrap();