diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_14_40.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_14_40.java
index f72bccbf2..18e671aeb 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_14_40.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_14_40.java
@@ -13,8 +13,6 @@ import org.hl7.fhir.r4.model.Type;
 
 public class BaseAdvisor_14_40 extends BaseAdvisor40<org.hl7.fhir.dstu2016may.model.Extension> {
 
-  final List<String> conformanceIgnoredUrls = Collections.singletonList("http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown");
-  private final List<String> ignoredUrls = new ArrayList<>(Collections.singletonList("http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown"));
   private final List<Class<?>> ignoredExtensionTypes = new ArrayList<>(Collections.singletonList(Expression.class));
 
   public BaseAdvisor_14_40() {
@@ -27,13 +25,8 @@ public class BaseAdvisor_14_40 extends BaseAdvisor40<org.hl7.fhir.dstu2016may.mo
 
   public boolean ignoreExtension(@Nonnull String path,
                                  @Nonnull String url) {
-    final List<String> paths = Arrays.asList(path.split(","));
-    final String lastPath = paths.get(paths.size() - 1);
-    if ((lastPath.equals("Conformance")) && (conformanceIgnoredUrls.contains(url))) {
-      return true;
-    } else {
-      return this.ignoredUrls.contains(url);
-    }
+    // no globally ignored extensions here.
+    return false;
   }
 
   public boolean ignoreType(@Nonnull String path, @Nonnull Type type) {
diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/VersionConvertor_14_40.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/VersionConvertor_14_40.java
index eb0d50d5c..12d4051dd 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/VersionConvertor_14_40.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/VersionConvertor_14_40.java
@@ -137,14 +137,18 @@ public class VersionConvertor_14_40 {
     }
   }
 
-  public void copyDomainResource(@Nonnull org.hl7.fhir.dstu2016may.model.DomainResource src,
-                                 @Nonnull org.hl7.fhir.r4.model.DomainResource tgt) throws FHIRException {
-    resourceConvertor.copyDomainResource(src, tgt);
+  public void copyDomainResource(
+    @Nonnull org.hl7.fhir.dstu2016may.model.DomainResource src,
+    @Nonnull org.hl7.fhir.r4.model.DomainResource tgt,
+    String... extensionUrlsToIgnore) throws FHIRException {
+    resourceConvertor.copyDomainResource(src, tgt, extensionUrlsToIgnore);
   }
 
-  public void copyDomainResource(@Nonnull org.hl7.fhir.r4.model.DomainResource src,
-                                 @Nonnull org.hl7.fhir.dstu2016may.model.DomainResource tgt) throws FHIRException {
-    resourceConvertor.copyDomainResource(src, tgt);
+  public void copyDomainResource(
+    @Nonnull org.hl7.fhir.r4.model.DomainResource src,
+    @Nonnull org.hl7.fhir.dstu2016may.model.DomainResource tgt,
+    String... extensionUrlsToIgnore) throws FHIRException {
+    resourceConvertor.copyDomainResource(src, tgt, extensionUrlsToIgnore);
   }
 
   public void copyElement(@Nonnull org.hl7.fhir.dstu2016may.model.Element src,
diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Conformance14_40.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Conformance14_40.java
index 29ac51302..12734273f 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Conformance14_40.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Conformance14_40.java
@@ -19,6 +19,12 @@ import org.hl7.fhir.r4.model.CapabilityStatement.CapabilityStatementRestResource
 
 public class Conformance14_40 {
 
+  public static final String ACCEPT_UNKNOWN_EXTENSION_URL = "http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown";
+
+  private static final String[] IGNORED_EXTENSION_URLS = new String[]{
+    ACCEPT_UNKNOWN_EXTENSION_URL
+  };
+
   static public org.hl7.fhir.r4.model.Enumeration<org.hl7.fhir.r4.model.CapabilityStatement.ConditionalDeleteStatus> convertConditionalDeleteStatus(org.hl7.fhir.dstu2016may.model.Enumeration<org.hl7.fhir.dstu2016may.model.Conformance.ConditionalDeleteStatus> src) throws FHIRException {
     if (src == null || src.isEmpty())
       return null;
@@ -67,7 +73,7 @@ public class Conformance14_40 {
     if (src == null || src.isEmpty())
       return null;
     org.hl7.fhir.dstu2016may.model.Conformance tgt = new org.hl7.fhir.dstu2016may.model.Conformance();
-    ConversionContext14_40.INSTANCE.getVersionConvertor_14_40().copyDomainResource(src, tgt);
+    ConversionContext14_40.INSTANCE.getVersionConvertor_14_40().copyDomainResource(src, tgt, IGNORED_EXTENSION_URLS);
     if (src.hasUrl())
       tgt.setUrlElement(Uri14_40.convertUri(src.getUrlElement()));
     if (src.hasVersion())
@@ -102,8 +108,8 @@ public class Conformance14_40 {
     if (src.hasImplementation())
       tgt.setImplementation(convertConformanceImplementationComponent(src.getImplementation()));
     tgt.setFhirVersion(src.getFhirVersion().toCode());
-    if (src.hasExtension("http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown"))
-      tgt.setAcceptUnknown(org.hl7.fhir.dstu2016may.model.Conformance.UnknownContentCode.fromCode(src.getExtensionByUrl("http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown").getValue().primitiveValue()));
+    if (src.hasExtension(ACCEPT_UNKNOWN_EXTENSION_URL))
+      tgt.setAcceptUnknown(org.hl7.fhir.dstu2016may.model.Conformance.UnknownContentCode.fromCode(src.getExtensionByUrl(ACCEPT_UNKNOWN_EXTENSION_URL).getValue().primitiveValue()));
     for (org.hl7.fhir.r4.model.CodeType t : src.getFormat()) tgt.addFormat(t.getValue());
     for (CapabilityStatementRestComponent r : src.getRest())
       for (CapabilityStatementRestResourceComponent rr : r.getResource())
@@ -159,7 +165,7 @@ public class Conformance14_40 {
     if (src.hasFhirVersion())
       tgt.setFhirVersion(org.hl7.fhir.r4.model.Enumerations.FHIRVersion.fromCode(src.getFhirVersion()));
     if (src.hasAcceptUnknown())
-      tgt.addExtension().setUrl("http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown").setValue(new org.hl7.fhir.r4.model.CodeType(src.getAcceptUnknownElement().asStringValue()));
+      tgt.addExtension().setUrl(ACCEPT_UNKNOWN_EXTENSION_URL).setValue(new org.hl7.fhir.r4.model.CodeType(src.getAcceptUnknownElement().asStringValue()));
     for (org.hl7.fhir.dstu2016may.model.CodeType t : src.getFormat()) tgt.addFormat(t.getValue());
     for (org.hl7.fhir.dstu2016may.model.Conformance.ConformanceRestComponent t : src.getRest())
       tgt.addRest(convertConformanceRestComponent(t));
diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Resource14_40.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Resource14_40.java
index 08477d722..6d3bb6b94 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Resource14_40.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv14_40/resources14_40/Resource14_40.java
@@ -7,6 +7,8 @@ import org.hl7.fhir.convertors.conv14_40.datatypes14_40.Meta14_40;
 import org.hl7.fhir.convertors.conv14_40.datatypes14_40.Narrative14_40;
 import org.hl7.fhir.exceptions.FHIRException;
 
+import java.util.Arrays;
+
 public class Resource14_40 {
 
   public final BaseAdvisor_14_40 advisor;
@@ -113,8 +115,10 @@ public class Resource14_40 {
     }
   }
 
-  public void copyDomainResource(org.hl7.fhir.dstu2016may.model.DomainResource src,
-                                 org.hl7.fhir.r4.model.DomainResource tgt) throws FHIRException {
+  public void copyDomainResource(
+    org.hl7.fhir.dstu2016may.model.DomainResource src,
+    org.hl7.fhir.r4.model.DomainResource tgt,
+    String... extensionUrlsToIgnore) throws FHIRException {
     copyResource(src, tgt);
     if (src.hasText()) tgt.setText(Narrative14_40.convertNarrative(src.getText()));
     src.getContained().stream()
@@ -125,7 +129,7 @@ public class Resource14_40 {
         org.hl7.fhir.r4.model.Extension convertExtension = new org.hl7.fhir.r4.model.Extension();
         advisor.handleExtension(ConversionContext14_40.INSTANCE.path(), extension, convertExtension);
         tgt.addExtension(convertExtension);
-      } else if (!advisor.ignoreExtension(ConversionContext14_40.INSTANCE.path(), extension)) {
+      } else if (!advisor.ignoreExtension(ConversionContext14_40.INSTANCE.path(), extension) && !Arrays.asList(extensionUrlsToIgnore).contains(extension.getUrl())) {
         tgt.addExtension(Extension14_40.convertExtension(extension));
       }
     });
@@ -135,8 +139,10 @@ public class Resource14_40 {
       .forEach(tgt::addModifierExtension);
   }
 
-  public void copyDomainResource(org.hl7.fhir.r4.model.DomainResource src,
-                                 org.hl7.fhir.dstu2016may.model.DomainResource tgt) throws FHIRException {
+  public void copyDomainResource(
+    org.hl7.fhir.r4.model.DomainResource src,
+    org.hl7.fhir.dstu2016may.model.DomainResource tgt,
+    String... extensionUrlsToIgnore) throws FHIRException {
     copyResource(src, tgt);
     if (src.hasText()) tgt.setText(Narrative14_40.convertNarrative(src.getText()));
     src.getContained().stream()
@@ -147,7 +153,7 @@ public class Resource14_40 {
         org.hl7.fhir.dstu2016may.model.Extension convertExtension = new org.hl7.fhir.dstu2016may.model.Extension();
         advisor.handleExtension(ConversionContext14_40.INSTANCE.path(), extension, convertExtension);
         tgt.addExtension(convertExtension);
-      } else if (!advisor.ignoreExtension(ConversionContext14_40.INSTANCE.path(), extension)) {
+      } else if (!advisor.ignoreExtension(ConversionContext14_40.INSTANCE.path(), extension) && !Arrays.asList(extensionUrlsToIgnore).contains(extension.getUrl())) {
         tgt.addExtension(Extension14_40.convertExtension(extension));
       }
     });