diff --git a/crates/core/src/value.rs b/crates/core/src/value.rs
index cfef7ac57..9a5c09bdf 100644
--- a/crates/core/src/value.rs
+++ b/crates/core/src/value.rs
@@ -359,6 +359,10 @@ pub fn number_to_text(n: f64) -> String {
     if !(1e-9..1e15).contains(&a) && a.round() != a || a >= 1e15 {
         return sci_text(n, 15);
     }
+    // A value just below 1e15 can round up to 1e15 at 15 significant digits.
+    if format!("{:.14e}", a).parse::<f64>().is_ok_and(|r| r >= 1e15) {
+        return sci_text(n, 15);
+    }
     // 15 significant digits, trailing zeros trimmed.
     let mag = a.log10().floor() as i32;
     let decimals = (14 - mag).clamp(0, 30) as usize;
@@ -402,6 +406,13 @@ mod tests {
         assert_eq!(number_to_text(1.0 / 3.0), "0.333333333333333");
     }
 
+    #[test]
+    fn number_text_rounds_up_to_scientific_boundary() {
+        assert_eq!(number_to_text(999999999999999.9), "1E+15");
+        assert_eq!(number_to_text(-999999999999999.9), "-1E+15");
+        assert_eq!(number_to_text(999999999999999.0), "999999999999999");
+    }
+
     #[test]
     fn coercion() {
         assert_eq!(Value::from("12").to_number(), Ok(12.0));