diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index f075a34f19c4..41613d869dfa 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -1078,6 +1078,23 @@ class IDLInterface(IDLObjectWithScope, IDLExposureMixins):
 
             specialMembersSeen[memberType] = member
 
+        if self.getExtendedAttribute("LegacyUnenumerableNamedProperties"):
+            # Check that we have a named getter.
+            if "named getters" not in specialMembersSeen:
+                raise WebIDLError(
+                    "Interface with [LegacyUnenumerableNamedProperties] does "
+                    "not have a named getter",
+                    [self.location])
+            ancestor = self.parent
+            while ancestor:
+                if ancestor.getExtendedAttribute("LegacyUnenumerableNamedProperties"):
+                    raise WebIDLError(
+                        "Interface with [LegacyUnenumerableNamedProperties] "
+                        "inherits from another interface with "
+                        "[LegacyUnenumerableNamedProperties]",
+                        [self.location, ancestor.location])
+                ancestor = ancestor.parent
+
         if self._isOnGlobalProtoChain:
             # Make sure we have no named setters, creators, or deleters
             for memberType in ["setter", "creator", "deleter"]:
@@ -1465,6 +1482,7 @@ class IDLInterface(IDLObjectWithScope, IDLExposureMixins):
                   identifier == "UnsafeInPrerendering" or
                   identifier == "LegacyEventInit" or
                   identifier == "ProbablyShortLivingObject" or
+                  identifier == "LegacyUnenumerableNamedProperties" or
                   identifier == "NonOrdinaryGetPrototypeOf"):
                 # Known extended attributes that do not take values
                 if not attr.noArguments():
diff --git a/dom/bindings/parser/tests/test_unenumerable_own_properties.py b/dom/bindings/parser/tests/test_unenumerable_own_properties.py
new file mode 100644
index 000000000000..d017d5ce0928
--- /dev/null
+++ b/dom/bindings/parser/tests/test_unenumerable_own_properties.py
@@ -0,0 +1,64 @@
+def WebIDLTest(parser, harness):
+
+    parser.parse(
+        """
+        interface Foo {};
+        [LegacyUnenumerableNamedProperties]
+        interface Bar : Foo {
+          getter long(DOMString name);
+        };
+        interface Baz : Bar {
+          getter long(DOMString name);
+        };
+        """);
+    results = parser.finish();
+    harness.check(len(results), 3, "Should have three interfaces")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [LegacyUnenumerableNamedProperties]
+            interface NoNamedGetter {
+            };
+        """)
+
+        results = parser.finish()
+    except Exception, x:
+        threw = True
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [LegacyUnenumerableNamedProperties=Foo]
+            interface ShouldNotHaveArg {
+              getter long(DOMString name);
+            };
+        """)
+
+        results = parser.finish()
+    except Exception, x:
+        threw = True
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            [LegacyUnenumerableNamedProperties]
+            interface Foo {
+              getter long(DOMString name);
+            };
+            interface Bar : Foo {};
+            [LegacyUnenumerableNamedProperties]
+            interface Baz : Bar {
+              getter long(DOMString name);
+            };
+        """)
+
+        results = parser.finish()
+    except Exception, x:
+        threw = True
+    harness.ok(threw, "Should have thrown.")