diff --git a/org.hl7.fhir.r4/src/main/resources/snapshot-generation-tests.xml b/org.hl7.fhir.r4/src/main/resources/snapshot-generation-tests.xml
index ba13ea65e..bc8e7c497 100644
--- a/org.hl7.fhir.r4/src/main/resources/snapshot-generation-tests.xml
+++ b/org.hl7.fhir.r4/src/main/resources/snapshot-generation-tests.xml
@@ -1838,40 +1838,25 @@
       <description value="fixture for #38: Constrained polymporphic elements"/>
       <kind value="resource"/>
       <abstract value="false"/>
-      <type value="MedicationDispense"/>
-      <baseDefinition value="http://hl7.org/fhir/StructureDefinition/MedicationDispense"/>
+      <type value="MedicationRequest"/>
+      <baseDefinition value="http://hl7.org/fhir/StructureDefinition/MedicationRequest"/>
       <derivation value="constraint"/>
       <differential>
         <element>
-          <path value="MedicationDispense"/>
+          <path value="MedicationRequest"/>
         </element>
         <element>
-          <path value="MedicationDispense.dosageInstruction"/>
+          <path value="MedicationRequest.dosageInstruction"/>
         </element>
         <element>
-          <!-- Including this element isn't strictly necessary to reproduce the problem.  However, its inclusion seemed to prevent certain errors from showing up when I trimmed the instance, so I'm leaving it in -->
-          <path value="MedicationDispense.dosageInstruction.extension"/>
-          <slicing>
-            <discriminator>
-              <type value="value"/>
-              <path value="url"/>
-            </discriminator>
-            <rules value="open"/>
-          </slicing>
+          <path value="MedicationRequest.dosageInstruction.timing"/>
+        </element>
+        <element>
+          <path value="MedicationRequiest.dosageInstruction.timing.event"/>
           <mustSupport value="true"/>
         </element>
         <element>
-          <path value="MedicationOrder.dosageInstruction.additionalInstruction"/>
-          <type>
-            <code value="Quantity"/>
-          </type>
-          <mustSupport value="true"/>
-        </element>
-        <element>
-          <path value="MedicationOrder.dosageInstruction.doseQuantity"/>
-          <type>
-            <code value="Quantity"/>
-          </type>
+          <path value="MedicationRequest.dosageInstruction.timing.repeat"/>
           <mustSupport value="true"/>
         </element>
       </differential>
@@ -3682,9 +3667,9 @@
     <action>
       <assert>
         <label value="test37"/>
-        <description value="Snapshot includes polymorphic constrained element"/>
+        <description value="Snapshot missing polymorphic constrained element from differential"/>
         <direction value="response"/>
-        <expression value="fixture('t37o').snapshot.element.where(path = 'MedicationDispense.dosageInstruction.doseQuantity').count() = 1"/>
+        <expression value="fixture('t37o').snapshot.element.where(path = 'MedicationRequest.dosageInstruction.timing.repeat').mustSupport"/>
         <warningOnly value="false"/>
       </assert>
     </action>