diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/FHIRLexer.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/FHIRLexer.java
index dc6c3785f..650fa30ed 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/FHIRLexer.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/utils/FHIRLexer.java
@@ -80,9 +80,9 @@ public class FHIRLexer {
   }
 
   public boolean isConstant() {
-    return current != null && (current.charAt(0) == '\'' || current.charAt(0) == '"') || current.charAt(0) == '@' || current.charAt(0) == '%' || 
+    return !Utilities.noString(current) && ((current.charAt(0) == '\'' || current.charAt(0) == '"') || current.charAt(0) == '@' || current.charAt(0) == '%' || 
         current.charAt(0) == '-' || current.charAt(0) == '+' || (current.charAt(0) >= '0' && current.charAt(0) <= '9') || 
-        current.equals("true") || current.equals("false") || current.equals("{}");
+        current.equals("true") || current.equals("false") || current.equals("{}"));
   }
 
   public boolean isFixedName() {
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 5f6906a0e..be2718d15 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
@@ -3102,7 +3102,13 @@ public class InstanceValidator extends BaseValidator implements IResourceValidat
             } else if (!criteriaElement.hasType() || criteriaElement.getType().size() == 1) {
               if (discriminator.contains("["))
                 discriminator = discriminator.substring(0, discriminator.indexOf('['));
-              type = criteriaElement.getType().get(0).getWorkingCode();
+              if (criteriaElement.hasType()) {
+                type = criteriaElement.getType().get(0).getWorkingCode();
+              } else if (!criteriaElement.getPath().contains(".")) {
+                type = criteriaElement.getPath();
+              } else {
+                throw new DefinitionException(context.formatMessage(I18nConstants.DISCRIMINATOR__IS_BASED_ON_TYPE_BUT_SLICE__IN__HAS_NO_TYPES, discriminator, ed.getId(), profile.getUrl()));
+              }
             } else if (criteriaElement.getType().size() > 1) {
               throw new DefinitionException(context.formatMessage(I18nConstants.DISCRIMINATOR__IS_BASED_ON_TYPE_BUT_SLICE__IN__HAS_MULTIPLE_TYPES_, discriminator, ed.getId(), profile.getUrl(), criteriaElement.typeSummary()));
             } else