diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_10_30.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_10_30.java
index 178a9cda3..9391cd1d1 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_10_30.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/advisors/impl/BaseAdvisor_10_30.java
@@ -10,8 +10,6 @@ import org.hl7.fhir.convertors.advisors.interfaces.BaseAdvisor30;
 
 public class BaseAdvisor_10_30 extends BaseAdvisor30<org.hl7.fhir.dstu2.model.Extension> {
 
-  private final List<String> ignoredUrls = new ArrayList<>(Collections.singletonList("http://hl7.org/fhir/3.0/StructureDefinition/extension-CapabilityStatement.acceptUnknown"));
-
   public BaseAdvisor_10_30() {
   }
 
@@ -21,6 +19,7 @@ public class BaseAdvisor_10_30 extends BaseAdvisor30<org.hl7.fhir.dstu2.model.Ex
 
   public boolean ignoreExtension(@Nonnull String path,
                                  @Nonnull String url) {
-    return this.ignoredUrls.contains(url);
+    // no globally ignored extensions here.
+    return false;
   }
 }
diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/VersionConvertor_10_30.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/VersionConvertor_10_30.java
index 44ad9714a..eb027841f 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/VersionConvertor_10_30.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/VersionConvertor_10_30.java
@@ -113,14 +113,19 @@ public class VersionConvertor_10_30 {
     }
   }
 
-  public void copyDomainResource(@Nonnull org.hl7.fhir.dstu2.model.DomainResource src,
-                                 @Nonnull org.hl7.fhir.dstu3.model.DomainResource tgt) throws FHIRException {
-    resourceConvertor.copyDomainResource(src, tgt);
+  public void copyDomainResource(
+    @Nonnull org.hl7.fhir.dstu2.model.DomainResource src,
+    @Nonnull org.hl7.fhir.dstu3.model.DomainResource tgt,
+    String ... extensionUrlsToIgnore
+    ) throws FHIRException {
+    resourceConvertor.copyDomainResource(src, tgt,extensionUrlsToIgnore);
   }
 
-  public void copyDomainResource(@Nonnull org.hl7.fhir.dstu3.model.DomainResource src,
-                                 @Nonnull org.hl7.fhir.dstu2.model.DomainResource tgt) throws FHIRException {
-    resourceConvertor.copyDomainResource(src, tgt);
+  public void copyDomainResource(
+    @Nonnull org.hl7.fhir.dstu3.model.DomainResource src,
+    @Nonnull org.hl7.fhir.dstu2.model.DomainResource tgt,
+    String ... extensionUrlsToIgnore) throws FHIRException {
+    resourceConvertor.copyDomainResource(src, tgt, extensionUrlsToIgnore);
   }
 
   public void copyElement(@Nonnull org.hl7.fhir.dstu2.model.Element src,
diff --git a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/resources10_30/Resource10_30.java b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/resources10_30/Resource10_30.java
index 829fd6281..63572dc2d 100644
--- a/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/resources10_30/Resource10_30.java
+++ b/org.hl7.fhir.convertors/src/main/java/org/hl7/fhir/convertors/conv10_30/resources10_30/Resource10_30.java
@@ -6,6 +6,8 @@ import org.hl7.fhir.convertors.conv10_30.datatypes10_30.Meta10_30;
 import org.hl7.fhir.convertors.conv10_30.datatypes10_30.Narrative10_30;
 import org.hl7.fhir.exceptions.FHIRException;
 
+import java.util.Arrays;
+
 public class Resource10_30 {
 
   public final BaseAdvisor_10_30 advisor;
@@ -14,26 +16,34 @@ public class Resource10_30 {
     this.advisor = advisor;
   }
 
-  public void copyDomainResource(org.hl7.fhir.dstu2.model.DomainResource src,
-                                 org.hl7.fhir.dstu3.model.DomainResource tgt) throws FHIRException {
+  public void copyDomainResource(
+    org.hl7.fhir.dstu2.model.DomainResource src,
+    org.hl7.fhir.dstu3.model.DomainResource tgt,
+    String ... extensionUrlsToIgnore) throws FHIRException {
     copyResource(src, tgt);
     tgt.setText(Narrative10_30.convertNarrative(src.getText()));
-    for (org.hl7.fhir.dstu2.model.Resource t : src.getContained()) tgt.addContained(convertResource(t));
-    for (org.hl7.fhir.dstu2.model.Extension t : src.getExtension())
-      tgt.addExtension(Extension10_30.convertExtension(t));
-    for (org.hl7.fhir.dstu2.model.Extension t : src.getModifierExtension())
-      tgt.addModifierExtension(Extension10_30.convertExtension(t));
+    for (org.hl7.fhir.dstu2.model.Resource containedResource : src.getContained()) tgt.addContained(convertResource(containedResource));
+    for (org.hl7.fhir.dstu2.model.Extension extension : src.getExtension())
+      if (!Arrays.asList(extensionUrlsToIgnore).contains(extension.getUrl()))
+        tgt.addExtension(Extension10_30.convertExtension(extension));
+
+    for (org.hl7.fhir.dstu2.model.Extension modifierExtension : src.getModifierExtension())
+      tgt.addModifierExtension(Extension10_30.convertExtension(modifierExtension));
   }
 
-  public void copyDomainResource(org.hl7.fhir.dstu3.model.DomainResource src,
-                                 org.hl7.fhir.dstu2.model.DomainResource tgt) throws FHIRException {
+  public void copyDomainResource(
+    org.hl7.fhir.dstu3.model.DomainResource src,
+    org.hl7.fhir.dstu2.model.DomainResource tgt,
+    String ... extensionUrlsToIgnore
+    ) throws FHIRException {
     copyResource(src, tgt);
     tgt.setText(Narrative10_30.convertNarrative(src.getText()));
-    for (org.hl7.fhir.dstu3.model.Resource t : src.getContained()) tgt.addContained(convertResource(t));
-    for (org.hl7.fhir.dstu3.model.Extension t : src.getExtension())
-      tgt.addExtension(Extension10_30.convertExtension(t));
-    for (org.hl7.fhir.dstu3.model.Extension t : src.getModifierExtension())
-      tgt.addModifierExtension(Extension10_30.convertExtension(t));
+    for (org.hl7.fhir.dstu3.model.Resource containedResource : src.getContained()) tgt.addContained(convertResource(containedResource));
+    for (org.hl7.fhir.dstu3.model.Extension extension : src.getExtension())
+      if (!Arrays.asList(extensionUrlsToIgnore).contains(extension.getUrl()))
+      tgt.addExtension(Extension10_30.convertExtension(extension));
+    for (org.hl7.fhir.dstu3.model.Extension modifierExtension : src.getModifierExtension())
+      tgt.addModifierExtension(Extension10_30.convertExtension(modifierExtension));
   }
 
   public void copyResource(org.hl7.fhir.dstu2.model.Resource src, org.hl7.fhir.dstu3.model.Resource tgt) throws FHIRException {