diff --git a/source/codesystem/operationdefinition-CodeSystem-validate-code.xml b/source/codesystem/operationdefinition-CodeSystem-validate-code.xml
index 82a82f5a2d..bb52be9702 100644
--- a/source/codesystem/operationdefinition-CodeSystem-validate-code.xml
+++ b/source/codesystem/operationdefinition-CodeSystem-validate-code.xml
@@ -144,6 +144,14 @@
     <documentation value="Specifies the language to be used for description when validating the display property"/>
     <type value="code"/>
   </parameter>
+  <parameter>
+    <name value="useSupplement"/>
+    <use value="in"/>
+    <min value="0"/>
+    <max value="*"/>
+    <documentation value="When using this input parameter, all provided supplements must be used when validating the display or properties of the concept code. Use of this parameter should result in $validate-code behaving the same way as if the supplements were included in an &quot;all codes&quot; value set definition using the [ValueSet Supplement](http://hl7.org/fhir/StructureDefinition/valueset-supplement) extension"/>
+    <type value="canonical"/>
+  </parameter>
   <parameter>
     <name value="result"/>
     <use value="out"/>
diff --git a/source/namingsystem/structuredefinition-NamingSystem.xml b/source/namingsystem/structuredefinition-NamingSystem.xml
index 4f8004e9cb..2fc45459f7 100644
--- a/source/namingsystem/structuredefinition-NamingSystem.xml
+++ b/source/namingsystem/structuredefinition-NamingSystem.xml
@@ -111,7 +111,7 @@
 				<key value="nsd-3"/>
 				<severity value="error"/>
 				<human value="Can't have more than one authoritative identifier for a type/period combination (only one authoritative identifier allowed at any given point of time)"/>
-				<expression value="uniqueId.where(authoritative = true).select(type.toString() &amp; period.start.toString() &amp; period.end.toString()).isDistinct()"/>
+				<expression value="uniqueId.where(authoritative and value = 'base').select(defineVariable('uId').select(%context..where($this != %uId and authoritative and type = %uId.type).where((period.start.empty() or %uId.period.end.empty() or period.start &lt;= %uId.period.end) and (%uId.period.start.empty() or period.end.empty() or %uId.period.start &lt;= period.end)).select(trace('error', %uId.value &amp; ' overlaps ' &amp; value)))).empty()"/>
 				<source value="http://hl7.org/fhir/StructureDefinition/NamingSystem"/>
 			</constraint>
 			<constraint>