diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
index 8b4fdddddf9d3..6ae4bfa335445 100644
--- a/dom/bindings/parser/WebIDL.py
+++ b/dom/bindings/parser/WebIDL.py
@@ -8668,7 +8668,6 @@ def reset(self):
 
     # Builtin IDL defined by WebIDL
     _builtins = """
-        typedef unsigned long long DOMTimeStamp;
         typedef (ArrayBufferView or ArrayBuffer) BufferSource;
     """
 
diff --git a/dom/bindings/parser/tests/test_builtins.py b/dom/bindings/parser/tests/test_builtins.py
index cd22c1678b300..a75a12e814367 100644
--- a/dom/bindings/parser/tests/test_builtins.py
+++ b/dom/bindings/parser/tests/test_builtins.py
@@ -14,7 +14,6 @@ def WebIDLTest(parser, harness):
           attribute unsigned long u32;
           attribute long long s64;
           attribute unsigned long long u64;
-          attribute DOMTimeStamp ts;
         };
     """
     )
@@ -32,7 +31,7 @@ def WebIDLTest(parser, harness):
     harness.check(iface.parent, None, "Interface has no parent")
 
     members = iface.members
-    harness.check(len(members), 10, "Should be one production")
+    harness.check(len(members), 9, "Should be one production")
 
     names = ["b", "s8", "u8", "s16", "u16", "s32", "u32", "s64", "u64", "ts"]
     types = [
@@ -47,7 +46,7 @@ def WebIDLTest(parser, harness):
         "UnsignedLongLong",
         "UnsignedLongLong",
     ]
-    for i in range(10):
+    for i in range(9):
         attr = members[i]
         harness.ok(isinstance(attr, WebIDL.IDLAttribute), "Should be an IDLAttribute")
         harness.check(
diff --git a/dom/imptests/idlharness.js b/dom/imptests/idlharness.js
index dbf13aa0c984a..b49e7dec4c720 100644
--- a/dom/imptests/idlharness.js
+++ b/dom/imptests/idlharness.js
@@ -416,6 +416,7 @@ IdlArray.prototype.assert_type_is = function(value, type)
             return;
 
         case "unsigned long long":
+        case "EpochTimeStamp":
         case "DOMTimeStamp":
             assert_equals(typeof value, "number");
             assert_true(0 <= value, "unsigned long long is negative");
diff --git a/dom/interfaces/base/domstubs.idl b/dom/interfaces/base/domstubs.idl
index 97acf9a0056a9..1f2ccfd57631f 100644
--- a/dom/interfaces/base/domstubs.idl
+++ b/dom/interfaces/base/domstubs.idl
@@ -11,7 +11,9 @@ class nsWrapperCache;
 
 [ptr] native nsWrapperCachePtr(nsWrapperCache);
 
+// DOMTimeStamp is deprecated, use EpochTimeStamp instead.
 typedef unsigned long long DOMTimeStamp;
+typedef unsigned long long EpochTimeStamp;
 typedef double DOMHighResTimeStamp;
 typedef unsigned long long nsViewID;
 
diff --git a/dom/webidl/Performance.webidl b/dom/webidl/Performance.webidl
index ee2b69b76f0cc..b3da02db281a9 100644
--- a/dom/webidl/Performance.webidl
+++ b/dom/webidl/Performance.webidl
@@ -14,6 +14,9 @@
  * W3C liability, trademark and document use rules apply.
  */
 
+// DOMTimeStamp is deprecated, use EpochTimeStamp instead.
+typedef unsigned long long DOMTimeStamp;
+typedef unsigned long long EpochTimeStamp;
 typedef double DOMHighResTimeStamp;
 typedef sequence <PerformanceEntry> PerformanceEntryList;