diff --git a/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/i18n/I18nConstants.java b/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/i18n/I18nConstants.java
index a961106212..c4494e86aa 100644
--- a/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/i18n/I18nConstants.java
+++ b/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/i18n/I18nConstants.java
@@ -955,6 +955,7 @@ public class I18nConstants {
   public static final String MSG_WITHDRAWN = "MSG_WITHDRAWN";
   public static final String MSG_RETIRED = "MSG_RETIRED";
   public static final String INACTIVE_CODE_WARNING = "INACTIVE_CODE_WARNING";
+  public static final String SD_EXTENSION_URL_MISSING = "SD_EXTENSION_URL_MISSING";
 }
 
 
diff --git a/org.hl7.fhir.utilities/src/main/resources/Messages.properties b/org.hl7.fhir.utilities/src/main/resources/Messages.properties
index 545e3ac014..5de2104e7b 100644
--- a/org.hl7.fhir.utilities/src/main/resources/Messages.properties
+++ b/org.hl7.fhir.utilities/src/main/resources/Messages.properties
@@ -1008,7 +1008,9 @@ FHIRPATH_COLLECTION_STATUS_OPERATION_RIGHT = The right side is inherently a coll
 FHIRPATH_OFTYPE_IMPOSSIBLE = The type specified in ofType is {1} which is not a possible candidate for the existing types ({0}) in the expression {2}. Check the paths and types to be sure this is what is intended
 ED_SEARCH_EXPRESSION_ERROR = Error in search expression ''{0}'': {1}
 SD_EXTENSION_URL_MISMATCH = The fixed value for the extension URL is {1} which doesn''t match the canonical URL {0}
+SD_EXTENSION_URL_MISSING = The value of Extension.url is not fixed to the extension URL {0}
 MSG_DEPRECATED = Reference to deprecated item {0}
 MSG_WITHDRAWN = Reference to withdrawn item {0}
 MSG_RETIRED = Reference to retired item {0}
 INACTIVE_CODE_WARNING = The code ''{0}'' is valid but is not active
+SD_ED_TYPE_PROFILE_WRONG_TYPE = The type {0} is not in the list of allowed types {1} in the profile {2}
diff --git a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/type/StructureDefinitionValidator.java b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/type/StructureDefinitionValidator.java
index b39da1e417..6ed6958fb1 100644
--- a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/type/StructureDefinitionValidator.java
+++ b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/type/StructureDefinitionValidator.java
@@ -169,7 +169,11 @@ public boolean validateStructureDefinition(List<ValidationMessage> errors, Eleme
         String baseD = src.getNamedChildValue("baseDefinition");
         if ("http://hl7.org/fhir/StructureDefinition/Extension".equals(baseD) && url != null) {
           String fixedUrl = getFixedValue(src);
-          ok = rule(errors, "2023-05-27", IssueType.INVALID, stack.getLiteralPath(), url.equals(fixedUrl), I18nConstants.SD_EXTENSION_URL_MISMATCH, url, fixedUrl) && ok;
+          if (rule(errors, "2023-08-05", IssueType.INVALID, stack.getLiteralPath(), fixedUrl != null, I18nConstants.SD_EXTENSION_URL_MISSING, url)) {
+            ok = rule(errors, "2023-08-05", IssueType.INVALID, stack.getLiteralPath(), url.equals(fixedUrl), I18nConstants.SD_EXTENSION_URL_MISMATCH, url, fixedUrl) && ok;
+          } else {
+            ok = false;
+          }
         }
       }
     } catch (Exception e) {