diff --git a/model/sample.go b/model/sample.go
index 5e2134a..12d22ec 100644
--- a/model/sample.go
+++ b/model/sample.go
@@ -47,6 +47,8 @@ func (s Samples) Less(i, j int) bool {
 	switch {
 	case s[i].Metric.Before(s[j].Metric):
 		return true
+	case s[j].Metric.Before(s[i].Metric):
+		return false
 	case s[i].Timestamp.Before(s[j].Timestamp):
 		return true
 	default:
diff --git a/model/sample_test.go b/model/sample_test.go
new file mode 100644
index 0000000..1e59266
--- /dev/null
+++ b/model/sample_test.go
@@ -0,0 +1,129 @@
+// Copyright 2013 Prometheus Team
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package model
+
+import (
+	"sort"
+	"testing"
+)
+
+func TestSamplesSort(t *testing.T) {
+	input := Samples{
+		&Sample{
+			// Fingerprint: 7658840550047852795
+			Metric: Metric{
+				MetricNameLabel: "B",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			// Fingerprint: 7658840550047852795
+			Metric: Metric{
+				MetricNameLabel: "B",
+			},
+			Timestamp: 2,
+		},
+		&Sample{
+			// Fingerprint: 13206712341014817019
+			Metric: Metric{
+				MetricNameLabel: "A",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			// Fingerprint: 13206712341014817019
+			Metric: Metric{
+				MetricNameLabel: "A",
+			},
+			Timestamp: 2,
+		},
+		&Sample{
+			// Fingerprint: 2110968759080888571
+			Metric: Metric{
+				MetricNameLabel: "C",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			// Fingerprint: 2110968759080888571
+			Metric: Metric{
+				MetricNameLabel: "C",
+			},
+			Timestamp: 2,
+		},
+	}
+
+	expected := Samples{
+		&Sample{
+			// Fingerprint: 2110968759080888571
+			Metric: Metric{
+				MetricNameLabel: "C",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			// Fingerprint: 2110968759080888571
+			Metric: Metric{
+				MetricNameLabel: "C",
+			},
+			Timestamp: 2,
+		},
+		&Sample{
+			// Fingerprint: 7658840550047852795
+			Metric: Metric{
+				MetricNameLabel: "B",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			// Fingerprint: 7658840550047852795
+			Metric: Metric{
+				MetricNameLabel: "B",
+			},
+			Timestamp: 2,
+		},
+		&Sample{
+			// Fingerprint: 13206712341014817019
+			Metric: Metric{
+				MetricNameLabel: "A",
+			},
+			Timestamp: 1,
+		},
+		&Sample{
+			// Fingerprint: 13206712341014817019
+			Metric: Metric{
+				MetricNameLabel: "A",
+			},
+			Timestamp: 2,
+		},
+	}
+
+	sort.Sort(input)
+
+	for i, actual := range input {
+		actualFp := Fingerprint{}
+		actualFp.LoadFromMetric(actual.Metric)
+
+		expectedFp := Fingerprint{}
+		expectedFp.LoadFromMetric(expected[i].Metric)
+
+		if !actualFp.Equal(&expectedFp) {
+			t.Fatalf("%d. Incorrect fingerprint. Got %s; want %s", i, actualFp, expectedFp)
+		}
+
+		if actual.Timestamp != expected[i].Timestamp {
+			t.Fatalf("%d. Incorrect timestamp. Got %s; want %s", i, actual.Timestamp, expected[i].Timestamp)
+		}
+	}
+}