diff --git a/crates/formula/src/lexer.rs b/crates/formula/src/lexer.rs
index f85fcde93..83ea78a86 100644
--- a/crates/formula/src/lexer.rs
+++ b/crates/formula/src/lexer.rs
@@ -338,12 +338,16 @@ pub fn tokenize_locale(src: &str, locale: crate::FormulaLocale) -> Result<Vec<To
                     push(&mut out, Tok::Sheet(w, None), j + 1);
                     i = j + 1;
                 } else if ch(j) == Some(':') && {
-                    // Sheet1:Sheet3!A1 — look ahead for word then '!'
+                    // Sheet1:Sheet3!A1 — look ahead for word then '!'.
                     let mut k = j + 1;
                     while ch(k).is_some_and(|c| is_word_char(c) && !(array_depth > 0 && c == locale.array_column_separator())) {
                         k += 1;
                     }
-                    k > j + 1 && ch(k) == Some('!')
+                    // `Sheet1!A1:Sheet1!B2` is a range whose second end repeats the sheet, not a span.
+                    let repeats_sheet = is_range_end(&w)
+                        && matches!(out.last(), Some(Token { tok: Tok::Sheet(p, None), .. })
+                            if chars.get(j + 1..k).is_some_and(|s| s.iter().map(|c| c.1).eq(p.chars())));
+                    k > j + 1 && ch(k) == Some('!') && !repeats_sheet
                 } {
                     let mut k = j + 1;
                     while ch(k).is_some_and(|c| is_word_char(c) && !(array_depth > 0 && c == locale.array_column_separator())) {
diff --git a/crates/formula/src/tests.rs b/crates/formula/src/tests.rs
index 822554923..2318a8b29 100644
--- a/crates/formula/src/tests.rs
+++ b/crates/formula/src/tests.rs
@@ -5,6 +5,13 @@ fn rt(src: &str) -> String {
     print(&parse(src).unwrap_or_else(|e| panic!("{src}: {e}")))
 }
 
+#[test]
+fn range_end_repeating_sheet_name_round_trips() {
+    assert_eq!(rt("'a'!A1:'a'!B2"), "a!A1:a!B2");
+    assert_eq!(rt("Sheet1!A1:Sheet1!B2"), "Sheet1!A1:Sheet1!B2");
+    assert_eq!(rt("SUM(a!A1:a!B2)"), "SUM(a!A1:a!B2)");
+}
+
 #[test]
 fn quoted_sheet_qualified_name_keeps_quotes() {
     assert_eq!(rt("'My Sheet'!Total"), "'My Sheet'!Total");
@@ -503,3 +510,9 @@ fn number_literal_too_large_for_f64_is_a_parse_error() {
     }
     assert!(parse("1E+308").is_ok());
 }
+
+#[test]
+fn three_d_span_and_cell_start_still_lex_as_span() {
+    assert_eq!(rt("SUM(Sheet1:Sheet3!A1)"), "SUM(Sheet1:Sheet3!A1)");
+    assert_eq!(rt("SUM(Q1:Sheet3!A1)"), "SUM('Q1:Sheet3'!A1)");
+}