diff --git a/release-notes.md b/release-notes.md
index b3d636a04..f34b6b1fb 100644
--- a/release-notes.md
+++ b/release-notes.md
@@ -1,7 +1,7 @@
 ## Change Notes:
 
-* 
+* Add support for code = / concept = filters on $expand
 
 ## Conformance Notes:
 
-* 
\ No newline at end of file
+* tx.fhir.org passed all HL7 terminology service tests (mode 'tx.fhir.org', tests v1.6.6, runner v6.4.0)
diff --git a/server/tx_server.pas b/server/tx_server.pas
index 52ab25186..deeb78f58 100644
--- a/server/tx_server.pas
+++ b/server/tx_server.pas
@@ -562,7 +562,7 @@ function TTerminologyServer.isKnownValueSet(id: String; out vs: TFhirValueSetW):
   if id.Contains('|') then
     id := id.Substring(0, id.IndexOf('|'));
 
-  if id.StartsWith('http://snomed.info/') then
+  if (CommonTerminologies.DefSnomed <> nil) and (id.StartsWith('http://snomed.info/')) then
   begin
     vs := CommonTerminologies.DefSnomed.buildValueSet(Factory, id);
     if (vs = nil) then
@@ -575,7 +575,7 @@ function TTerminologyServer.isKnownValueSet(id: String; out vs: TFhirValueSetW):
       end;
     end;
   end
-  else if id.StartsWith('http://loinc.org/vs/LP') or id.StartsWith('http://loinc.org/vs/LL') then
+  else if (CommonTerminologies.Loinc <> nil) and (id.StartsWith('http://loinc.org/vs/LP') or id.StartsWith('http://loinc.org/vs/LL')) then
     vs := CommonTerminologies.Loinc.buildValueSet(Factory, id)
   else if id = 'http://loinc.org/vs' then
     vs := CommonTerminologies.Loinc.buildValueSet(Factory, '')