diff --git a/Ghidra/Features/Decompiler/src/decompile/cpp/type.cc b/Ghidra/Features/Decompiler/src/decompile/cpp/type.cc
index a55ab8d038..963b36f982 100644
--- a/Ghidra/Features/Decompiler/src/decompile/cpp/type.cc
+++ b/Ghidra/Features/Decompiler/src/decompile/cpp/type.cc
@@ -3083,7 +3083,7 @@ Datatype *TypeFactory::findAdd(Datatype &ct)
 
   if (ct.name.size()!=0) {	// If there is a name
     if (ct.id == 0)		// There must be an id
-      throw LowlevelError("Datatype must have a valid id");
+      throw LowlevelError("Datatype must have a valid id: "+ct.name);
     res = findByIdLocal(ct.name,ct.id); // Lookup type by it
     if (res != (Datatype *)0) { // If a type has this name
       if (0!=res->compareDependency( ct )) // Check if it is the same type
diff --git a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/PcodeDataTypeManager.java b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/PcodeDataTypeManager.java
index 2207edb9e0..9b9c3c1dc9 100644
--- a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/PcodeDataTypeManager.java
+++ b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/PcodeDataTypeManager.java
@@ -1215,7 +1215,7 @@ public class PcodeDataTypeManager {
 	}
 
 	/**
-	 * Encode the coretypes to the stream
+	 * Encode the core data-types to the stream
 	 * @param encoder is the stream encoder
 	 * @throws IOException for errors in the underlying stream
 	 */
@@ -1233,8 +1233,7 @@ public class PcodeDataTypeManager {
 			if (typeMap.isUtf) {
 				encoder.writeBool(ATTRIB_UTF, true);
 			}
-			// Encode special id ( <0 for builtins )
-			encoder.writeSignedInteger(ATTRIB_ID, typeMap.id);
+			encoder.writeUnsignedInteger(ATTRIB_ID, typeMap.id);
 			encoder.closeElement(ELEM_TYPE);
 		}
 		encoder.closeElement(ELEM_CORETYPES);