diff --git a/prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadata.java b/prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadata.java
index b9e577e2c..8a393cf95 100644
--- a/prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadata.java
+++ b/prometheus-metrics-model/src/main/java/io/prometheus/metrics/model/snapshots/MetricMetadata.java
@@ -107,7 +107,7 @@ private void validate() {
         }
         if (hasUnit()) {
             if (!name.endsWith("_" + unit) && !name.endsWith("." + unit)) {
-                throw new IllegalArgumentException("'" + name + "': Illegal metric name. The name must end with _" + unit + "."
+                throw new IllegalArgumentException("'" + name + "': Illegal metric name. If the unit is non-null, the name must end with the unit: _" + unit + "."
                         + " Call " + PrometheusNaming.class.getSimpleName() + ".sanitizeMetricName(name, unit) to avoid this error.");
             }
         }
diff --git a/prometheus-metrics-model/src/test/java/io/prometheus/metrics/model/snapshots/MetricMetadataTest.java b/prometheus-metrics-model/src/test/java/io/prometheus/metrics/model/snapshots/MetricMetadataTest.java
index 77a328873..f9e9a18d6 100644
--- a/prometheus-metrics-model/src/test/java/io/prometheus/metrics/model/snapshots/MetricMetadataTest.java
+++ b/prometheus-metrics-model/src/test/java/io/prometheus/metrics/model/snapshots/MetricMetadataTest.java
@@ -54,4 +54,19 @@ public void testSanitizationWeirdCornerCase() {
     public void testSanitizeEmptyString() {
         sanitizeMetricName("");
     }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testUnitSuffixRequired() {
+        new MetricMetadata("my_counter", "help", Unit.SECONDS);
+    }
+
+    @Test
+    public void testUnitSuffixAdded() {
+        new MetricMetadata(sanitizeMetricName("my_counter", Unit.SECONDS), "help", Unit.SECONDS);
+    }
+
+    @Test
+    public void testUnitNotDuplicated() {
+        Assert.assertEquals("my_counter_bytes", sanitizeMetricName("my_counter_bytes", Unit.BYTES));
+    }
 }