diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 79de3973e..0e2d6cfb3 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1 +1,2 @@
-* https://github.com/hapifhir/org.hl7.fhir.core/issues/602
+* https://github.com/hapifhir/org.hl7.fhir.core/issues/499
+* https://github.com/hapifhir/org.hl7.fhir.core/issues/602
diff --git a/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/model/ExpressionNode.java b/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/model/ExpressionNode.java
index 3ed27a087..ab53186f7 100644
--- a/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/model/ExpressionNode.java
+++ b/org.hl7.fhir.r4/src/main/java/org/hl7/fhir/r4/model/ExpressionNode.java
@@ -1,33 +1,33 @@
 package org.hl7.fhir.r4.model;
 
-/*
-  Copyright (c) 2011+, HL7, Inc.
-  All rights reserved.
-  
-  Redistribution and use in source and binary forms, with or without modification, 
-  are permitted provided that the following conditions are met:
-    
-   * Redistributions of source code must retain the above copyright notice, this 
-     list of conditions and the following disclaimer.
-   * Redistributions in binary form must reproduce the above copyright notice, 
-     this list of conditions and the following disclaimer in the documentation 
-     and/or other materials provided with the distribution.
-   * Neither the name of HL7 nor the names of its contributors may be used to 
-     endorse or promote products derived from this software without specific 
-     prior written permission.
-  
-  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
-  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
-  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
-  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
-  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
-  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
-  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
-  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
-  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
-  POSSIBILITY OF SUCH DAMAGE.
-  
- */
+/*
+  Copyright (c) 2011+, HL7, Inc.
+  All rights reserved.
+  
+  Redistribution and use in source and binary forms, with or without modification, 
+  are permitted provided that the following conditions are met:
+    
+   * Redistributions of source code must retain the above copyright notice, this 
+     list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above copyright notice, 
+     this list of conditions and the following disclaimer in the documentation 
+     and/or other materials provided with the distribution.
+   * Neither the name of HL7 nor the names of its contributors may be used to 
+     endorse or promote products derived from this software without specific 
+     prior written permission.
+  
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
+  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
+  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
+  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
+  POSSIBILITY OF SUCH DAMAGE.
+  
+ */
 
 
 
@@ -331,43 +331,46 @@ public class ExpressionNode {
 	public String toString() {
 		StringBuilder b = new StringBuilder();
 		switch (kind) {
-		case Name:
-			b.append(name);
-			break;
-		case Function:
-			if (function == Function.Item) 
-				b.append("[");
-			else {
-				b.append(name);
-				b.append("(");
-			}
-			boolean first = true;
-			for (ExpressionNode n : parameters) {
-				if (first)
-					first = false;
-				else
-					b.append(", ");
-				b.append(n.toString());
-			}
-			if (function == Function.Item) 
-				b.append("]");
-			else {
-				b.append(")");
-			}
+      case Name:
+        b.append(name);
+        break;
+      case Function:
+        if (function == Function.Item)
+          b.append("[");
+        else {
+          b.append(name);
+          b.append("(");
+        }
+        boolean first = true;
+        for (ExpressionNode n : parameters) {
+          if (first)
+            first = false;
+          else
+            b.append(", ");
+          b.append(n.toString());
+        }
+        if (function == Function.Item) {
+          b.append("]");
+        } else {
+          b.append(")");
+        }
 			break;
 		case Constant:
-		  if (constant instanceof StringType)
-	      b.append("'"+Utilities.escapeJson(constant.primitiveValue())+"'");
-		  else if (constant instanceof Quantity) {
+      if (constant == null) {
+        b.append("{}");
+      } else if (constant instanceof StringType) {
+        b.append("'" + Utilities.escapeJson(constant.primitiveValue()) + "'");
+      } else if (constant instanceof Quantity) {
 		    Quantity q = (Quantity) constant;
         b.append(Utilities.escapeJson(q.getValue().toPlainString()));
         b.append(" '");
         b.append(Utilities.escapeJson(q.getUnit()));
         b.append("'");
-		  } else if (constant.primitiveValue() != null)
-		    b.append(Utilities.escapeJson(constant.primitiveValue()));
-		  else 
+		  } else if (constant.primitiveValue() != null) {
+        b.append(Utilities.escapeJson(constant.primitiveValue()));
+      } else {
         b.append(Utilities.escapeJson(constant.toString()));
+      }
 			break;
 		case Group:
 			b.append("(");
diff --git a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/ExpressionNode.java b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/ExpressionNode.java
index 92f1c17cb..0bffff94b 100644
--- a/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/ExpressionNode.java
+++ b/org.hl7.fhir.r5/src/main/java/org/hl7/fhir/r5/model/ExpressionNode.java
@@ -1,33 +1,33 @@
 package org.hl7.fhir.r5.model;
 
-/*
-  Copyright (c) 2011+, HL7, Inc.
-  All rights reserved.
-  
-  Redistribution and use in source and binary forms, with or without modification, 
-  are permitted provided that the following conditions are met:
-    
-   * Redistributions of source code must retain the above copyright notice, this 
-     list of conditions and the following disclaimer.
-   * Redistributions in binary form must reproduce the above copyright notice, 
-     this list of conditions and the following disclaimer in the documentation 
-     and/or other materials provided with the distribution.
-   * Neither the name of HL7 nor the names of its contributors may be used to 
-     endorse or promote products derived from this software without specific 
-     prior written permission.
-  
-  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
-  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
-  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
-  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
-  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
-  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
-  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
-  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
-  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
-  POSSIBILITY OF SUCH DAMAGE.
-  
- */
+/*
+  Copyright (c) 2011+, HL7, Inc.
+  All rights reserved.
+  
+  Redistribution and use in source and binary forms, with or without modification, 
+  are permitted provided that the following conditions are met:
+    
+   * Redistributions of source code must retain the above copyright notice, this 
+     list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above copyright notice, 
+     this list of conditions and the following disclaimer in the documentation 
+     and/or other materials provided with the distribution.
+   * Neither the name of HL7 nor the names of its contributors may be used to 
+     endorse or promote products derived from this software without specific 
+     prior written permission.
+  
+  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
+  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
+  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
+  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
+  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
+  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
+  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
+  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
+  POSSIBILITY OF SUCH DAMAGE.
+  
+ */
 
 
 
@@ -395,25 +395,28 @@ public class ExpressionNode {
 					b.append(", ");
 				b.append(n.toString());
 			}
-			if (function == Function.Item) 
-				b.append("]");
-			else {
+			if (function == Function.Item) {
+        b.append("]");
+      } else {
 				b.append(")");
 			}
 			break;
 		case Constant:
-		  if (constant instanceof StringType)
-	      b.append("'"+Utilities.escapeJson(constant.primitiveValue())+"'");
-		  else if (constant instanceof Quantity) {
+      if (constant == null) {
+        b.append("{}");
+      } else if (constant instanceof StringType) {
+        b.append("'" + Utilities.escapeJson(constant.primitiveValue()) + "'");
+      } else if (constant instanceof Quantity) {
 		    Quantity q = (Quantity) constant;
         b.append(Utilities.escapeJson(q.getValue().toPlainString()));
         b.append(" '");
         b.append(Utilities.escapeJson(q.getUnit()));
         b.append("'");
-		  } else if (constant.primitiveValue() != null)
-		    b.append(Utilities.escapeJson(constant.primitiveValue()));
-		  else 
+		  } else if (constant.primitiveValue() != null) {
+        b.append(Utilities.escapeJson(constant.primitiveValue()));
+      } else {
         b.append(Utilities.escapeJson(constant.toString()));
+      }
 			break;
 		case Group:
 			b.append("(");