diff --git a/Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/pe/PEx64UnwindInfoDataType.java b/Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/pe/PEx64UnwindInfoDataType.java
index f6b71959d8..da43861fbe 100644
--- a/Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/pe/PEx64UnwindInfoDataType.java
+++ b/Ghidra/Features/Base/src/main/java/ghidra/app/util/bin/format/pe/PEx64UnwindInfoDataType.java
@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -164,7 +164,7 @@ public class PEx64UnwindInfoDataType extends DynamicDataType {
 
 	private static EnumDataType unwindInfoFlagsEnum;
 
-	private EnumDataType defineUnwindInfoFlags() {
+	private synchronized EnumDataType defineUnwindInfoFlags() {
 		if (unwindInfoFlagsEnum == null) {
 			unwindInfoFlagsEnum = new EnumDataType("UNW_FLAGS", 1);
 			unwindInfoFlagsEnum.add("UNW_FLAG_NHANDLER", PEx64UnwindInfo.UNW_FLAG_NHANDLER);
diff --git a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/data/EnumDataType.java b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/data/EnumDataType.java
index 60934ecf4d..102e19d3f1 100644
--- a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/data/EnumDataType.java
+++ b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/data/EnumDataType.java
@@ -4,9 +4,9 @@
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
- * 
+ *
  *      http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -130,6 +130,7 @@ public class EnumDataType extends GenericDataType implements Enum {
 		List<String> names = new ArrayList<>();
 		Collection<List<String>> values = valueMap.values();
 		for (List<String> list : values) {
+			list = new ArrayList<>(list);
 			Collections.sort(list);
 			names.addAll(list);
 		}