diff --git a/src/promql/src/range_eval/function.rs b/src/promql/src/range_eval/function.rs
index f48ea7a469e..6ebe3aa23ad 100644
--- a/src/promql/src/range_eval/function.rs
+++ b/src/promql/src/range_eval/function.rs
@@ -184,11 +184,14 @@ fn quantile(q: f64, values: &[f64], sorted: &mut Vec<f64>) -> f64 {
     }
     sorted.clear();
     sorted.extend_from_slice(values);
-    sorted.sort_unstable_by(|a, b| match (a.is_nan(), b.is_nan()) {
+    // Go's `vectorByValueHeap` puts NaN first and treats +0 and -0 as equal; Go sorts short
+    // inputs by insertion, which keeps equal values in window order, and which zero is picked
+    // decides the sign of the result.
+    sorted.sort_by(|a, b| match (a.is_nan(), b.is_nan()) {
         (true, true) => std::cmp::Ordering::Equal,
         (true, false) => std::cmp::Ordering::Less,
         (false, true) => std::cmp::Ordering::Greater,
-        (false, false) => a.total_cmp(b),
+        (false, false) => a.partial_cmp(b).expect("neither is NaN"),
     });
     let n = sorted.len() as f64;
     let rank = q * (n - 1.0);
diff --git a/src/promql/src/range_eval/tests.rs b/src/promql/src/range_eval/tests.rs
index 0a129f6f814..5e26eb39f23 100644
--- a/src/promql/src/range_eval/tests.rs
+++ b/src/promql/src/range_eval/tests.rs
@@ -27,7 +27,9 @@ use datatypes::series::histogram::{
     BucketSideView, CounterResetHint, HistogramBatchBuilder, HistogramView,
 };
 use datatypes::series::raw::{RawSeriesChunk, RawTimestamps};
-use datatypes::series::samples::{FieldSpec, Samples, Series, SeriesFields, SeriesSchema};
+use datatypes::series::samples::{
+    FieldSpec, SampleRef, Samples, Series, SeriesFields, SeriesSchema,
+};
 use datatypes::series::time::{EvalGrid, GridSpec};
 use datatypes::series::{Label, MetricName};
 use rand::rngs::StdRng;
@@ -986,3 +988,29 @@ fn waiting_for_a_point_drops_samples_behind_its_window() {
     let last = chunk(&[(100_000, vec![Some(1.0)])], 1, 0, true);
     assert!(evaluator.push(&last).unwrap().is_some());
 }
+
+/// Equal values keep window order in `quantile_over_time`, so the zero a quantile lands on is
+/// the one Prometheus picks: `1 / quantile_over_time(1, m[3s])` over +0, -0, -0 is -Inf.
+#[test]
+fn quantile_keeps_the_window_order_of_signed_zeros() {
+    let window = RangeWindow {
+        range_ms: 3_000,
+        offset_ms: 0,
+        anchor_ms: None,
+    };
+    let rows: Vec<Row> = [(0, 0.0), (1_000, -0.0), (2_000, -0.0)]
+        .map(|(ts, value)| (ts, vec![Some(value)]))
+        .to_vec();
+    let mut evaluator = RangeEvaluator::try_new(
+        &raw_schema(1),
+        grid(2_000, 1_000, 1),
+        window,
+        RangeFunction::QuantileOverTime(1.0),
+    )
+    .unwrap();
+    let series = evaluator.push(&chunk(&rows, 1, 0, true)).unwrap().unwrap();
+    let SampleRef::Float(value) = series.fields.as_slice()[0].sample(0) else {
+        panic!("expected a float");
+    };
+    assert_eq!(1.0 / value, f64::NEG_INFINITY);
+}