diff --git a/SDT/schema4.0/etc/domain.rnc b/SDT/schema4.0/etc/domain.rnc
index 948cf751ad71f83a5d28634928f7c63169d0b961..ca1ff61fae8225b7fec32288ca171ea03ce7fd92 100644
--- a/SDT/schema4.0/etc/domain.rnc
+++ b/SDT/schema4.0/etc/domain.rnc
@@ -137,7 +137,10 @@ ProductsDef =
       PropertiesDef?,
       ModuleClassesDef?,
       SubDevicesRef?,
-      element DeviceClass { ExtendDef },
+      element DeviceClass {
+        # TODO: Make optional?
+        ExtendDef
+      },
       ExtendDef?
     }+
   }
@@ -205,7 +208,6 @@ ExtendType =
   | "datapoint"
   | "event"
   | "moduleclass"
-  | "product"
   | "property"
   | "device"
   | "subdevice"
diff --git a/SDT/schema4.0/src/domain.rng b/SDT/schema4.0/src/domain.rng
index e8b3a98def1397e9a0d6ddd09b094fe041dd04c7..b614d10ac4d4a980ebf6ca18da572fdf96c24ef8 100644
--- a/SDT/schema4.0/src/domain.rng
+++ b/SDT/schema4.0/src/domain.rng
@@ -388,7 +388,7 @@
 					<optional>
 						<ref name="SubDevicesRef" />
 					</optional>
-					<element name="DeviceClass">
+					<element name="DeviceClass">  <!-- TODO: Make optional? -->
 						<ref name="ExtendDef" />
 					</element>
 					<optional>
@@ -570,7 +570,6 @@
 			<value>datapoint</value>
 			<value>event</value>
 			<value>moduleclass</value>
-			<value>product</value>
 			<value>property</value>
 			<value>device</value>
 			<value>subdevice</value>
diff --git a/SDT/schema4.0/src/domain.xsd b/SDT/schema4.0/src/domain.xsd
index f0c20b3c92da5e3be0fcaaa6fa1fc536db8faadf..b2e85762f033a8f2fefa73d65917f8f0555c8991 100644
--- a/SDT/schema4.0/src/domain.xsd
+++ b/SDT/schema4.0/src/domain.xsd
@@ -423,7 +423,6 @@
       <xs:enumeration value="datapoint"/>
       <xs:enumeration value="event"/>
       <xs:enumeration value="moduleclass"/>
-      <xs:enumeration value="product"/>
       <xs:enumeration value="property"/>
       <xs:enumeration value="device"/>
       <xs:enumeration value="subdevice"/>