diff --git a/prometheus/src/main/scala/filodb/prometheus/ast/Vectors.scala b/prometheus/src/main/scala/filodb/prometheus/ast/Vectors.scala
index e95fd1b7bb..e0fd105299 100644
--- a/prometheus/src/main/scala/filodb/prometheus/ast/Vectors.scala
+++ b/prometheus/src/main/scala/filodb/prometheus/ast/Vectors.scala
@@ -8,9 +8,10 @@ import filodb.prometheus.parse.Parser
 import filodb.query._
 
 object Vectors {
-  val PromMetricLabel = "__name__"
-  val TypeLabel       = "_type_"
-  val BucketFilterLabel = "_bucket_"
+  val PromMetricLabel         = "__name__"
+  val PromInternalMetricLabel = "_metric_"
+  val TypeLabel               = "_type_"
+  val BucketFilterLabel       = "_bucket_"
 }
 
 object WindowConstants {
@@ -151,7 +152,7 @@ sealed trait Vector extends Expression {
    *   (2) at least one label matcher exists.
    */
   def applyPromqlConstraints(): Unit = {
-    val nameLabel = labelSelection.find(_.label == PromMetricLabel)
+    val nameLabel = labelSelection.find(lm => lm.label == PromMetricLabel || lm.label == PromInternalMetricLabel)
     if (metricName.nonEmpty) {
       if (nameLabel.nonEmpty) {
         throw new IllegalArgumentException(
diff --git a/prometheus/src/test/scala/filodb/prometheus/parse/ParserSpec.scala b/prometheus/src/test/scala/filodb/prometheus/parse/ParserSpec.scala
index 5b57e6a5bb..305f6fb3f5 100644
--- a/prometheus/src/test/scala/filodb/prometheus/parse/ParserSpec.scala
+++ b/prometheus/src/test/scala/filodb/prometheus/parse/ParserSpec.scala
@@ -181,10 +181,15 @@ class ParserSpec extends AnyFunSpec with Matchers {
     parseError("foo{a*\"b\"}")
     parseError("foo{a>=\"b\"}")
 
+    parseSuccessfully("{__name__=\"foo\"}")
+    parseSuccessfully("{_metric_=\"foo\"}")
     parseError("foo::b{gibberish}")
     parseError("foo{1}")
     parseError("{}")
     parseError("foo{__name__=\"bar\"}")
+    parseError("foo{__name__=\"foo\"}")
+    parseError("foo{_metric_=\"bar\"}")
+    parseError("foo{_metric_=\"foo\"}")
 
     parseSuccessfully("test{a=\"b\"}[5y] OFFSET 3d")
     parseSuccessfully("test{a=\"b\"}[5y] LIMIT 3")
@@ -728,6 +733,7 @@ class ParserSpec extends AnyFunSpec with Matchers {
       ("""{__name__="foo"}""" -> Map("__name__" -> "foo")),
       ("""{__name__="foo", bar="baz"}""" -> Map("__name__" -> "foo", "bar" -> "baz")),
       ("""{bar="baz"}""" -> Map("bar" -> "baz")),
+      """{_metric_="foo"}"""  ->  Map("_metric_" -> "foo"),    // not same as """{__name__="foo"}"""
       ("""foo{bar="baz", bog="bah"}""" -> Map("__name__" -> "foo", "bar" -> "baz", "bog" -> "bah")),
     )