diff --git a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeManagerDB.java b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeManagerDB.java
index 73d45f4e85..81310f47f5 100644
--- a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeManagerDB.java
+++ b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/database/data/DataTypeManagerDB.java
@@ -1111,7 +1111,9 @@ abstract public class DataTypeManagerDB implements DataTypeManager {
 		}
 		else {
 			buildSortedDataTypeList();
-			Iterator<DataType> it = sortedDataTypes.iterator();
+			// make copy of sortedDataTypes list before iterating as dt.dataTypeReplaced may 
+			// call back into this class and cause a modification to the sortedDataTypes list.
+			Iterator<DataType> it = new ArrayList<>(sortedDataTypes).iterator();
 			while (it.hasNext()) {
 				DataType dt = it.next();
 				dt.dataTypeReplaced(existingDt, newDt);
diff --git a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/DynamicHash.java b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/DynamicHash.java
index 75cc6157e6..8fb24b73e1 100644
--- a/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/DynamicHash.java
+++ b/Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/pcode/DynamicHash.java
@@ -118,8 +118,8 @@ public class DynamicHash {
 			reg = SimpleCRC32.hashOneByte(reg, slot);
 			reg = SimpleCRC32.hashOneByte(reg, transtable[op.getOpcode()]);
 			long val = op.getSeqnum().getTarget().getOffset();
-			int sz = op.getSeqnum().getTarget().getPointerSize();
-			for (int i = 0; i < sz; ++i) {
+			int sz = op.getSeqnum().getTarget().getSize();
+			for (int i = 0; i < sz; i += 8) {
 				reg = SimpleCRC32.hashOneByte(reg, (int) val);
 				val >>= 8;
 			}
diff --git a/Ghidra/Framework/Utility/src/main/java/ghidra/GhidraLauncher.java b/Ghidra/Framework/Utility/src/main/java/ghidra/GhidraLauncher.java
index c21a749dd7..381dc1ad25 100644
--- a/Ghidra/Framework/Utility/src/main/java/ghidra/GhidraLauncher.java
+++ b/Ghidra/Framework/Utility/src/main/java/ghidra/GhidraLauncher.java
@@ -56,7 +56,7 @@ public class GhidraLauncher {
 			addExternalJarPaths(classpathList, layout.getApplicationRootDirs());
 		}
 		else {
-			addPatchPaths(classpathList, layout.getApplicationRootDirs());
+			addPatchPaths(classpathList, layout.getApplicationInstallationDir());
 			addModuleJarPaths(classpathList, layout.getModules());
 		}
 		classpathList = orderClasspath(classpathList);
@@ -79,25 +79,16 @@ public class GhidraLauncher {
 	}
 
 	/**
-	 * Add bin patch directories and lib patch jars to the given path list.  This should be done
+	 * Add patch jars to the given path list.  This should be done
 	 * first so they take precedence in the classpath.
 	 * 
 	 * @param pathList The list of paths to add to.
 	 * @param appRootDirs The application root directories to search.
 	 */
-	private static void addPatchPaths(List<String> pathList, Collection<ResourceFile> appRootDirs) {
-
-		for (ResourceFile rootDir : appRootDirs) {
-
-			ResourceFile dir = new ResourceFile(rootDir, "bin");
-			if (dir.exists()) {
-				pathList.add(dir.getAbsolutePath());
-			}
-
-			ResourceFile debugLibDir = new ResourceFile(rootDir, "lib");
-			if (debugLibDir.exists()) {
-				pathList.addAll(findJarsInDir(debugLibDir));
-			}
+	private static void addPatchPaths(List<String> pathList, ResourceFile installDir) {
+		ResourceFile patchDir = new ResourceFile(installDir, "Ghidra/patch");
+		if (patchDir.exists()) {
+			pathList.addAll(findJarsInDir(patchDir));
 		}
 	}
 
diff --git a/GhidraBuild/patch/README.txt b/GhidraBuild/patch/README.txt
new file mode 100644
index 0000000000..c80aadd7a0
--- /dev/null
+++ b/GhidraBuild/patch/README.txt
@@ -0,0 +1,3 @@
+Drop jar files in this directory to apply patches to an installation of Ghidra.  Any jar files
+found in this directory will be placed at the front of the classpath, allowing them to override
+any existing classes in any module.
\ No newline at end of file
diff --git a/GhidraBuild/patch/certification.local.manifest b/GhidraBuild/patch/certification.local.manifest
new file mode 100644
index 0000000000..6018e9ca9f
--- /dev/null
+++ b/GhidraBuild/patch/certification.local.manifest
@@ -0,0 +1,2 @@
+##VERSION: 2.0
+README.txt||GHIDRA||||END|
diff --git a/gradleScripts/distribution.gradle b/gradleScripts/distribution.gradle
index 15260c088c..10b6289462 100644
--- a/gradleScripts/distribution.gradle
+++ b/gradleScripts/distribution.gradle
@@ -394,7 +394,14 @@ task assembleCommon (type: Copy) {
 		into "Ghidra"
 		filter (ConcatFilter, prepend: buildDateFile)
 	}
-		
+
+	////////////////
+	// Patch Readme
+	////////////////
+	from (ROOT_PROJECT_DIR + "/GhidraBuild/patch") {
+		into "Ghidra/patch"
+	}		
+	
 	/////////////////
 	// GLOBALS
 	/////////////////