diff --git a/nodel-jyhost/build.gradle b/nodel-jyhost/build.gradle
index 9cb02055..eba33a55 100644
--- a/nodel-jyhost/build.gradle
+++ b/nodel-jyhost/build.gradle
@@ -62,7 +62,7 @@ dependencies {
     compile project(':nodel-framework')
     compile 'commons-daemon:commons-daemon:1.0.15'
     compile 'org.slf4j:slf4j-api:1.7.10'
-    compile 'org.python:jython-standalone:2.5.4-rc1'
+    compile 'org.python:jython-standalone:2.7.3'
 
     // for the Nodel HTTP client:
     compile group: 'org.apache.httpcomponents', name: 'httpclient', version: '4.5.5'
diff --git a/nodel-jyhost/src/main/java/org/nodel/jyhost/PyNode.java b/nodel-jyhost/src/main/java/org/nodel/jyhost/PyNode.java
index de16a9f9..0a20776f 100644
--- a/nodel-jyhost/src/main/java/org/nodel/jyhost/PyNode.java
+++ b/nodel-jyhost/src/main/java/org/nodel/jyhost/PyNode.java
@@ -22,6 +22,7 @@
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.concurrent.locks.ReentrantLock;
+import java.lang.reflect.Method;
 
 import org.joda.time.DateTime;
 import org.nodel.DateTimes;
@@ -71,6 +72,7 @@
 import org.python.core.PyDictionary;
 import org.python.core.PyException;
 import org.python.core.PyFunction;
+import org.python.core.PyInteger;
 import org.python.core.PyObject;
 import org.python.core.PyString;
 import org.python.core.PySystemState;
@@ -549,16 +551,6 @@ private void applyConfig0(NodeConfig config) throws Exception {
         
         _logger.info("Initialising new Python interpreter...");
         
-        PySystemState pySystemState = new PySystemState();
-
-        // set the current working directory
-        pySystemState.setCurrentWorkingDir(_root.getAbsolutePath());
-        
-        // append the Node's root directory to the path
-        pySystemState.path.append(new PyString(_root.getAbsolutePath()));
-        pySystemState.path.append(new PyString(_metaRoot.getAbsolutePath()));
-        Py.setSystemState(pySystemState);
-        
         _globals = new PyDictionary();
         
         ReentrantLock lock = null;
@@ -568,7 +560,6 @@ private void applyConfig0(NodeConfig config) throws Exception {
             
             trackFunction("(instance creation)");
 
-            // _python = new PythonInterpreter(globals, pySystemState);
             _python = PythonInterpreter.threadLocalStateInterpreter(_globals);
 
         } finally {
@@ -625,10 +616,10 @@ private void applyConfig0(NodeConfig config) throws Exception {
                 lock = getAReentrantLock();
                 
                 trackFunction("(toolkit injection)");
-                
+
                 // use this import to provide a toolkit directly into the script
                 _python.exec("from nodetoolkit import *");
-                
+
             } finally {
                 untrackFunction("(toolkit injection)");
                 
@@ -742,28 +733,34 @@ private void applyConfig0(NodeConfig config) throws Exception {
                     List<String> commentary = new ArrayList<>(3);
 
                     trackFunction("mains");
-                    
+
                     // handle @before_main functions (if present)
-                    PyFunction processBeforeMainFunctions = (PyFunction) _globals.get(Py.java2py("processBeforeMainFunctions"));
-                    long beforeFnCount = processBeforeMainFunctions.__call__().asLong();
-                    
-                    if (beforeFnCount > 0)
+                    if (_globals.get(Py.java2py("processBeforeMainFunctions")) instanceof PyFunction) {
+                        PyFunction processBeforeMainFunctions = (PyFunction) _globals.get(Py.java2py("processBeforeMainFunctions"));
+                        long beforeFnCount = processBeforeMainFunctions.__call__().asLong();
+
+                        if (beforeFnCount > 0)
                         commentary.add("'@before_main' function" + (beforeFnCount == 1 ? "" : "s"));
-                    
-                    // call 'main' if it exists
-                    PyFunction mainFunction = (PyFunction) _python.get("main");
-                    if (mainFunction != null) {
+                    }
+
+                    // handle main function (if present)
+                    if (_python.get("main") instanceof PyFunction) {
+                        PyFunction mainFunction = (PyFunction) _python.get("main");
+                        if (mainFunction != null) {
                         mainFunction.__call__();
 
                         commentary.add("'main'");
+                        }
                     }
-                    
+
                     // handle @after_main functions (if present)
-                    PyFunction processAfterMainFunctions = (PyFunction) _globals.get(Py.java2py("processAfterMainFunctions"));
-                    long afterFnCount = processAfterMainFunctions.__call__().asLong();
-                    if (afterFnCount > 0)
+                    if (_globals.get(Py.java2py("processAfterMainFunctions")) instanceof PyFunction) {
+                        PyFunction processAfterMainFunctions = (PyFunction) _globals.get(Py.java2py("processAfterMainFunctions"));
+                        long afterFnCount = processAfterMainFunctions.__call__().asLong();
+                        if (afterFnCount > 0)
                         commentary.add("'@after_main' function" + (afterFnCount == 1 ? "" : "s"));
-                    
+                    }
+
 
                     // nothing went wrong, kick off toolkit
                     _toolkit.enable();
@@ -889,8 +886,13 @@ public void error(Object obj) {
         
         // inject into 'sys'
         _pySystemState.__setattr__("nodetoolkit", Py.java2py(_toolkit));
+
+        // set the current working directory
+        _pySystemState.setCurrentWorkingDir(_root.getAbsolutePath());
         
-        
+        // append the Node's root directory to the path
+        _pySystemState.path.append(new PyString(_root.getAbsolutePath()));
+        _pySystemState.path.append(new PyString(_metaRoot.getAbsolutePath()));
     }
 
     /**
@@ -904,21 +906,23 @@ private void cleanupInterpreter() {
 
             _logger.info(message);
             _outReader.inject(message);
-            
+
             try {
-                PyFunction processCleanupFunctions = (PyFunction) _globals.get(Py.java2py("processCleanupFunctions"));
-                long cleanupFnCount = processCleanupFunctions.__call__().asLong();
-                
-                if (cleanupFnCount > 0) {
-                    message = "('@at_cleanup' function" + (cleanupFnCount == 1 ? "" : "s") + " completed.)";
-                    _logger.info(message);
-                    _outReader.inject(message);
+                if (_globals.get(Py.java2py("processCleanupFunctions")) instanceof PyFunction) {
+                    PyFunction processCleanupFunctions = (PyFunction) _globals.get(Py.java2py("processCleanupFunctions"));
+                    long cleanupFnCount = processCleanupFunctions.__call__().asLong();
+
+                    if (cleanupFnCount > 0) {
+                        message = "('@at_cleanup' function" + (cleanupFnCount == 1 ? "" : "s") + " completed.)";
+                        _logger.info(message);
+                        _outReader.inject(message);
+                    }
                 }
             } catch (Exception exc) {
                 // upstream exception handling should mean we never get here, but just in case
                 _logger.warn("Unexpected exception during cleaning up; should be safe to ignore", exc);
             }
-            
+
             _python.cleanup();
             
             message = "(clean up complete)";
@@ -1062,9 +1066,11 @@ protected Object handleActionRequest(SimpleName action, Object arg) {
                 
                 throw new IllegalStateException("Action call failure (internal server error) - '" + functionName + "'");
             }
-            
+
             PyFunction pyFunction = (PyFunction) pyObject;
-            PyBaseCode code = (PyBaseCode) pyFunction.func_code;
+            PyBaseCode code = null;
+            Class<?> objectClass = pyFunction.getClass();
+            code = (PyBaseCode) objectClass.getField("__code__").get(pyFunction);
 
             // only support either 0 or 1 args
             PyObject pyResult;
@@ -1332,7 +1338,9 @@ private void handleRemoteEventArrival(SimpleName alias, NodelClientEvent nodelCl
             }
 
             PyFunction pyFunction = (PyFunction) pyObject;
-            PyBaseCode code = (PyBaseCode) pyFunction.func_code;
+            PyBaseCode code = null;
+            Class<?> objectClass = pyFunction.getClass();
+            code = (PyBaseCode) objectClass.getField("__code__").get(pyFunction);
 
             // only support either 0 or 1 args
             if (code.co_argcount == 0)