diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/JsonParser.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/JsonParser.java
index 527d98881..f84ac9929 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/JsonParser.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/elementmodel/JsonParser.java
@@ -59,6 +59,7 @@ import org.hl7.fhir.r5.model.Extension;
 import org.hl7.fhir.r5.model.StructureDefinition;
 import org.hl7.fhir.r5.utils.FHIRPathEngine;
 import org.hl7.fhir.r5.utils.ToolingExtensions;
+import org.hl7.fhir.utilities.CommaSeparatedStringBuilder;
 import org.hl7.fhir.utilities.StringPair;
 import org.hl7.fhir.utilities.TextFile;
 import org.hl7.fhir.utilities.Utilities;
@@ -301,18 +302,18 @@ public class JsonParser extends ParserBase {
       String code = property.getJsonKeyProperty();
       List<Property> properties = property.getChildProperties(element.getName(), null);
       if (properties.size() != 2) {
-        logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_CHILD_COUNT), IssueSeverity.ERROR);               
+        logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_CHILD_COUNT, propNames(properties)), IssueSeverity.ERROR);               
       } else {
         Property propK = properties.get(0);
         Property propV = properties.get(1);
         if (!propK.getName().equals(code)) {
-          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_NAME), IssueSeverity.ERROR);                       
+          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_NAME, propNames(properties)), IssueSeverity.ERROR);                       
         } else if (!propK.isPrimitive())  {
-          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_TYPE), IssueSeverity.ERROR);                       
+          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_TYPE, propNames(properties), propK.typeSummary()), IssueSeverity.ERROR);                       
         } else if (propV.isList())  {
-          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_NO_LIST), IssueSeverity.ERROR);                       
+          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_NO_LIST, propV.getName()), IssueSeverity.ERROR);                       
         } else if (propV.isChoice())  {
-          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_NO_CHOICE), IssueSeverity.ERROR);                       
+          logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.OBJECT_CANNOT_BE_KEYED_ARRAY_NO_CHOICE, propV.getName()), IssueSeverity.ERROR);                       
         } else if (!(e instanceof JsonObject)) {
           logError(line(e), col(e), npath, IssueType.INVALID, context.formatMessage(I18nConstants.THIS_PROPERTY_MUST_BE_AN_OBJECT_NOT_, describe(e)), IssueSeverity.ERROR);                       
         } else {
@@ -355,6 +356,14 @@ public class JsonParser extends ParserBase {
     }
   }
 
+  private Object propNames(List<Property> properties) {
+    CommaSeparatedStringBuilder b = new CommaSeparatedStringBuilder();
+    for (Property p: properties) {
+      b.append(p.getName());
+    }
+    return b.toString();
+  }
+
   private String describeType(JsonElement e) {
     if (e.isJsonArray())
       return "an Array";
diff --git a/org.hl7.fhir.utilities/src/main/resources/Messages.properties b/org.hl7.fhir.utilities/src/main/resources/Messages.properties
index 381fb34c1..0e4e27b07 100644
--- a/org.hl7.fhir.utilities/src/main/resources/Messages.properties
+++ b/org.hl7.fhir.utilities/src/main/resources/Messages.properties
@@ -383,11 +383,11 @@ This_property_must_be_an_object_not_ = This property must be an object, not {0}
 This_property_must_be_an_simple_value_not_ = This property must be an simple value, not {0} ({1} at {2})
 This_property_must_be__not_ = The property {2} must be {0}, not {1} (at {3})
 This_property_must_be_an_Array_not_ = The property {1}  must be a JSON Array, not {0} (at {2})
-OBJECT_CANNOT_BE_KEYED_ARRAY_CHILD_COUNT = This object cannot be an keyed Array in Json because it does not have two children in the definitions            
-OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_NAME = This object is defined as a keyed Array in Json but the definition does not name the first child element as the key
-OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_TYPE = This object is defined as a keyed Array in Json but the key property named in the definitions is not a primitive type
-OBJECT_CANNOT_BE_KEYED_ARRAY_NO_CHOICE = This object is defined as a keyed Array in Json but the value property named in the definitions is a choice - this is not supported
-OBJECT_CANNOT_BE_KEYED_ARRAY_NO_LIST = This object is defined as a keyed Array in Json but the value property named in the definitions is a list - this is not supported
+OBJECT_CANNOT_BE_KEYED_ARRAY_CHILD_COUNT = This object cannot be an keyed Array in Json because it does not have two children in the definitions (children = {0})            
+OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_NAME = This object is defined as a keyed Array in Json but the definition does not name the first child element as the key (children = {0})    
+OBJECT_CANNOT_BE_KEYED_ARRAY_PROP_TYPE = This object is defined as a keyed Array in Json but the key property named in the definitions is not a primitive type (children = {0}, type = {1})    
+OBJECT_CANNOT_BE_KEYED_ARRAY_NO_CHOICE = This object is defined as a keyed Array in Json but the value property named in the definitions is a choice - this is not supported (value property = {0})    
+OBJECT_CANNOT_BE_KEYED_ARRAY_NO_LIST = This object is defined as a keyed Array in Json but the value property named in the definitions is a list - this is not supported (value property = {0}) 
 Unrecognised_property_ = Unrecognized property ''{0}''
 Object_must_have_some_content = Object must have some content
 Error_parsing_JSON_ = Error parsing JSON: {0}