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 4e4fbecce..d258606dc 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
@@ -331,6 +331,7 @@ public class I18nConstants {
   public static final String REFERENCE_REF_NOTFOUND_BUNDLE = "Reference_REF_NotFound_Bundle";
   public static final String REFERENCE_REF_NOTYPE = "Reference_REF_NoType";
   public static final String REFERENCE_REF_RESOURCETYPE = "Reference_REF_ResourceType";
+  public static final String REFERENCE_REF_SUSPICIOUS = "REFERENCE_REF_SUSPICIOUS";
   public static final String REFERENCE_REF_WRONGTARGET = "Reference_REF_WrongTarget";
   public static final String REFERENCE_TO__CANNOT_BE_RESOLVED = "reference_to__cannot_be_resolved";
   public static final String REFERENCE__REFERS_TO_A__NOT_A_VALUESET = "Reference__refers_to_a__not_a_ValueSet";
diff --git a/org.hl7.fhir.utilities/src/main/resources/Messages.properties b/org.hl7.fhir.utilities/src/main/resources/Messages.properties
index 481342e10..a72555b61 100644
--- a/org.hl7.fhir.utilities/src/main/resources/Messages.properties
+++ b/org.hl7.fhir.utilities/src/main/resources/Messages.properties
@@ -604,3 +604,4 @@ FHIRPATH_BAD_DATE = Unable to parse Date {0}
 FHIRPATH_NUMERICAL_ONLY = Error evaluating FHIRPath expression: The function {0} can only be used on integer, decimal or Quantity but found {1}
 FHIRPATH_DECIMAL_ONLY = Error evaluating FHIRPath expression: The function {0} can only be used on a decimal but found {1}
 FHIRPATH_FOCUS_PLURAL = Error evaluating FHIRPath expression: focus for {0} has more than one value
+REFERENCE_REF_SUSPICIOUS = The syntax of the reference ''{0}'' looks incorrect, and it should be checked
diff --git a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/InstanceValidator.java b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/InstanceValidator.java
index 48179bc5e..517b06b11 100644
--- a/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/InstanceValidator.java
+++ b/org.hl7.fhir.validation/src/main/java/org/hl7/fhir/validation/instance/InstanceValidator.java
@@ -2398,6 +2398,7 @@ public class InstanceValidator extends BaseValidator implements IResourceValidat
       // special known URLs that can't be validated but are known to be valid
       return;
     }
+    warning(errors, IssueType.STRUCTURE, element.line(), element.col(), path, !isSuspiciousReference(ref), I18nConstants.REFERENCE_REF_SUSPICIOUS, ref);      
 
     ResolvedReference we = localResolve(ref, stack, errors, path, (Element) hostContext.getAppContext(), element);
     String refType;
@@ -2439,10 +2440,11 @@ public class InstanceValidator extends BaseValidator implements IResourceValidat
     }
 
     String ft;
-    if (we != null)
+    if (we != null) {
       ft = we.getType();
-    else
+    } else {
       ft = tryParse(ref);
+    }
 
     if (reference.hasType()) { // R4 onwards...
       // the type has to match the specified
@@ -2596,6 +2598,20 @@ public class InstanceValidator extends BaseValidator implements IResourceValidat
     }
   }
 
+  private boolean isSuspiciousReference(String url) {
+    if (!assumeValidRestReferences || url == null || Utilities.isAbsoluteUrl(url)) {
+      return false;
+    }
+    String[] parts = url.split("\\/");
+    if (parts.length == 2 && context.getResourceNames().contains(parts[0]) && Utilities.isValidId(parts[1])) {
+      return false;
+    }
+    if (parts.length == 4 && context.getResourceNames().contains(parts[0]) && Utilities.isValidId(parts[1]) && "_history".equals(parts[2]) && Utilities.isValidId(parts[3])) {
+      return false;
+    }
+    return true;
+  }
+
   private String asListByUrl(Collection<StructureDefinition> list) {
     CommaSeparatedStringBuilder b = new CommaSeparatedStringBuilder();
     for (StructureDefinition sd : list) {
@@ -4842,7 +4858,7 @@ public class InstanceValidator extends BaseValidator implements IResourceValidat
       case 2:
         return checkResourceType(parts[0]);
       default:
-        if (parts[parts.length - 2].equals("_history"))
+        if (parts[parts.length - 2].equals("_history") && parts.length >= 4)
           return checkResourceType(parts[parts.length - 4]);
         else
           return checkResourceType(parts[parts.length - 2]);