diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ValueSetRenderer.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ValueSetRenderer.java
index 139ef9028..a18097ec2 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ValueSetRenderer.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/renderers/ValueSetRenderer.java
@@ -108,6 +108,9 @@ public class ValueSetRenderer extends TerminologyRenderer {
         ConceptMap cm = (ConceptMap) md;
         if (isSource(vs, cm.getSourceScope())) {
           ConceptMapRenderInstructions re = findByTarget(cm.getTargetScope());
+          if (re == null) {
+            re = new ConceptMapRenderInstructions(cm.present(), cm.getUrl(), false);
+          }
           if (re != null) {
             ValueSet vst = cm.hasTargetScope() ? getContext().getWorker().fetchResource(ValueSet.class, cm.hasTargetScopeCanonicalType() ? cm.getTargetScopeCanonicalType().getValue() : cm.getTargetScopeUriType().asStringValue()) : null;
             res.add(new UsedConceptMap(re, vst == null ? cm.getUserString("path") : vst.getUserString("path"), cm));
@@ -346,12 +349,14 @@ public class ValueSetRenderer extends TerminologyRenderer {
       return null;
     }
     String src = source.primitiveValue();
-    if (src != null)
-      for (ConceptMapRenderInstructions t : renderingMaps) {
-        if (src.equals(t.getUrl()))
-          return t;
-      }
-    return null;
+    if (src == null) {
+      return null;
+    }
+    for (ConceptMapRenderInstructions t : renderingMaps) {
+      if (src.equals(t.getUrl()))
+        return t;
+    }
+    return null;    
   }
 
 
diff --git a/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/CommaSeparatedStringBuilder.java b/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/CommaSeparatedStringBuilder.java
index 89c2eec92..c4c917595 100644
--- a/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/CommaSeparatedStringBuilder.java
+++ b/org.hl7.fhir.utilities/src/main/java/org/hl7/fhir/utilities/CommaSeparatedStringBuilder.java
@@ -44,23 +44,45 @@ public class CommaSeparatedStringBuilder {
   String sep = ", ";
   StringBuilder b = new StringBuilder();
   int count = 0;
+  String pending = null;
+  private String lastSep;
 
   public CommaSeparatedStringBuilder() {
+    this.sep = ", ";
+    this.lastSep = ", ";
   }
   
   public CommaSeparatedStringBuilder(String sep) {
     this.sep = sep;
+    this.lastSep = sep;
   }
 
+  public CommaSeparatedStringBuilder(String sep, String lastSep) {
+    this.sep = sep;
+    this.lastSep = lastSep;
+  }
+
+  private void commit(boolean last) {
+    if (pending != null) {
+      if (!first) {
+        if (last) {
+          b.append(lastSep);
+        } else {
+          b.append(sep);
+        }
+      }
+      b.append(pending);
+      first = false;  
+    }
+  }
   public void append(String value) {
-    if (!first)
-      b.append(sep);
-    b.append(value);
-    first = false;
+    commit(false);
+    pending = value;
     count++;    
   }
   
   public int length() {
+    commit(false);
     return b.length();
   }
   
@@ -70,6 +92,7 @@ public class CommaSeparatedStringBuilder {
 
   @Override
   public String toString() {
+    commit(true);
     return b.toString();
   }
 
@@ -81,7 +104,7 @@ public class CommaSeparatedStringBuilder {
 
   public void addAll(List<String> list) {
     for (String s : list) {
-      append(s);
+      appendIfNotNull(s);
     }
     
   }