diff --git a/lib/sandbox.js b/lib/sandbox.js
index 317f9cb..8cbd9a0 100644
--- a/lib/sandbox.js
+++ b/lib/sandbox.js
@@ -31,38 +31,29 @@ const COMMIT = Symbol();
 // Used to execute extensions and restart
 const EXT = Symbol();
 
-const sandbox = {
-  timestamp: null,
-  deviceData: null,
-  revision: null,
-  maxRevision: null,
-  uncommitted: false,
-  declarations: null,
-  extensionsCache: null,
-  extensions: null,
-  clear: null,
-  rng: null,
-  context: vm.createContext()
-}
+const context = vm.createContext();
+
+let state;
+
 
 class SandboxDate {
   constructor(arg) {
     if (arguments.length)
       return new (Function.prototype.bind.apply(Date, arguments));
 
-    return new Date(sandbox.timestamp);
+    return new Date(state.sessionContext.timestamp);
   }
 
   static now() {
-    return sandbox.timestamp;
+    return state.sessionContext.timestamp;
   }
 };
 
 function random() {
-  if (!sandbox.rng)
-    sandbox.rng = seedrandom(sandbox.timestamp);
+  if (!state.rng)
+    state.rng = seedrandom(sessionContext.timestamp);
 
-  return sandbox.rng();
+  return state.rng();
 }
 
 
@@ -70,18 +61,18 @@ class ParameterWrapper {
   constructor(path, attributes, unpacked, unpackedRevision) {
     for (let attrName of attributes) {
       Object.defineProperty(this, attrName, {get: function() {
-        if (sandbox.uncommitted)
+        if (state.uncommitted)
           commit();
 
-        if (sandbox.revision !== unpackedRevision) {
-          unpackedRevision = sandbox.revision;
-          unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
+        if (state.revision !== unpackedRevision) {
+          unpackedRevision = state.revision;
+          unpacked = device.unpack(state.sessionContext.deviceData, path, state.revision + 1);
         }
 
         if (!unpacked.length)
           return undefined;
 
-        let attr = sandbox.deviceData.attributes.get(unpacked[0], sandbox.revision + 1)[attrName];
+        let attr = state.sessionContext.deviceData.attributes.get(unpacked[0], state.revision + 1)[attrName];
 
         if (!attr)
           return undefined;
@@ -91,27 +82,27 @@ class ParameterWrapper {
     }
 
     Object.defineProperty(this, "path", {get: function() {
-      if (sandbox.uncommitted)
+      if (state.uncommitted)
         commit();
 
-      if (sandbox.revision !== unpackedRevision) {
-        unpackedRevision = sandbox.revision;
-        unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
+      if (state.revision !== unpackedRevision) {
+        unpackedRevision = state.revision;
+        unpacked = device.unpack(state.sessionContext.deviceData, path, state.revision + 1);
       }
 
       if (!unpacked.length)
         return undefined;
 
-      return unpacked[0].join('.');
+      return unpacked[0].join(".");
     }});
 
     Object.defineProperty(this, "size", {get: function() {
-      if (sandbox.uncommitted)
+      if (state.uncommitted)
         commit();
 
-      if (sandbox.revision !== unpackedRevision) {
-        unpackedRevision = sandbox.revision;
-        unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
+      if (state.revision !== unpackedRevision) {
+        unpackedRevision = state.revision;
+        unpacked = device.unpack(state.sessionContext.deviceData, path, state.revision + 1);
       }
 
       if (!unpacked.length)
@@ -121,23 +112,23 @@ class ParameterWrapper {
     }});
 
     this[Symbol.iterator] = function*() {
-      if (sandbox.uncommitted)
+      if (state.uncommitted)
         commit();
 
-      if (sandbox.revision !== unpackedRevision) {
-        unpackedRevision = sandbox.revision;
-        unpacked = device.unpack(sandbox.deviceData, path, sandbox.revision + 1);
+      if (state.revision !== unpackedRevision) {
+        unpackedRevision = state.revision;
+        unpacked = device.unpack(state.sessionContext.deviceData, path, state.revision + 1);
       }
 
       for (let p of unpacked)
-        yield new ParameterWrapper(p, attributes, [p], sandbox.revision);
+        yield new ParameterWrapper(p, attributes, [p], state.revision);
     }
   }
 }
 
 
 function declare(path, timestamps, values) {
-  sandbox.uncommitted = true;
+  state.uncommitted = true;
   if (!timestamps)
     timestamps = {};
 
@@ -175,55 +166,53 @@ function declare(path, timestamps, values) {
     }
   }
 
-  sandbox.declarations.push(declaration);
+  state.declarations.push(declaration);
 
   return new ParameterWrapper(parsedPath, Object.keys(attrs));
 }
 
 
 function clear(path, timestamp, attributes) {
-  sandbox.uncommitted = true;
+  state.uncommitted = true;
 
-  if (sandbox.revision === sandbox.maxRevision) {
-    sandbox.clear = sandbox.clear || [];
-    sandbox.clear.push([common.parsePath(path), timestamp, attributes]);
-  }
+  if (state.revision === maxRevision)
+    state.clear.push([common.parsePath(path), timestamp, attributes]);
 }
 
 
 function commit() {
-  ++ sandbox.revision;
-  sandbox.uncommitted = false;
+  ++ state.revision;
+  state.uncommitted = false;
 
-  if (sandbox.revision === sandbox.maxRevision + 1)
+  if (state.revision === state.maxRevision + 1)
     throw COMMIT;
-  else if (sandbox.revision > sandbox.maxRevision + 1)
+  else if (state.revision > state.maxRevision + 1)
     throw new Error("Declare function should not be called from within a try/catch block");
 }
 
 
 function ext() {
   let extCall = Array.from(arguments).map(String);
-  let key = `${sandbox.revision}: ${JSON.stringify(extCall)}`;
+  let key = `${state.revision}: ${JSON.stringify(extCall)}`;
 
-  if (key in sandbox.extensionsCache)
-    return sandbox.extensionsCache[key];
+  if (key in state.sessionContext.extensionsCache)
+    return state.sessionContext.extensionsCache[key];
 
-  sandbox.extensions[key] = extCall;
+  state.extensions[key] = extCall;
   throw EXT;
 }
 
 
-Object.defineProperty(sandbox.context, 'Date', {value: SandboxDate});
-Object.defineProperty(sandbox.context, 'declare', {value: declare});
-Object.defineProperty(sandbox.context, 'clear', {value: clear});
-Object.defineProperty(sandbox.context, 'commit', {value: commit});
-Object.defineProperty(sandbox.context, 'ext', {value: ext});
+Object.defineProperty(context, "Date", {value: SandboxDate});
+Object.defineProperty(context, "declare", {value: declare});
+Object.defineProperty(context, "clear", {value: clear});
+Object.defineProperty(context, "commit", {value: commit});
+Object.defineProperty(context, "ext", {value: ext});
 
 // Monkey-patch Math.random() to make it deterministic
-sandbox.context.random = random;
-vm.runInContext("Math.random = random;", sandbox.context);
-delete sandbox.random;
+context.random = random;
+vm.runInContext("Math.random = random;", context);
+delete context.random;
 
 
 function errorToFault(err) {
@@ -245,28 +234,27 @@ function errorToFault(err) {
 }
 
 
-function run(script, globals, timestamp, deviceData, extensionsCache, startRevision, maxRevision, callback) {
-  sandbox.timestamp = timestamp;
-  sandbox.deviceData = deviceData;
-  sandbox.extensionsCache = extensionsCache;
-  sandbox.revision = startRevision;
-  sandbox.maxRevision = maxRevision;
-  sandbox.uncommitted = false;
-  sandbox.declarations = [];
-  sandbox.extensions = {};
-  sandbox.clear = null;
-  sandbox.rng = null;
+function run(script, globals, sessionContext, startRevision, maxRevision, callback) {
+  state = {
+    sessionContext: sessionContext,
+    revision: startRevision,
+    maxRevision: maxRevision,
+    uncommitted: false,
+    declarations: [],
+    extensions: {},
+    clear: [],
+    rng: null
+  };
 
-  for (let n in sandbox.context)
-    delete sandbox.context[n];
+  for (let n of Object.keys(context))
+    delete context[n];
 
-  for (let n in globals)
-    sandbox.context[n] = globals[n];
+  Object.assign(context, globals);
 
   let ret, status;
 
   try {
-    ret = script.runInContext(sandbox.context, {displayErrors: false});
+    ret = script.runInContext(context, {displayErrors: false});
     status = 0;
   }
   catch (err) {
@@ -278,27 +266,24 @@ function run(script, globals, timestamp, deviceData, extensionsCache, startRevis
       return callback(null, errorToFault(err));
   }
 
-  let ext = sandbox.extensions;
-  let decs = sandbox.declarations;
-  let clr = sandbox.clear;
-  let extCache = sandbox.extensionsCache;
+  let _state = state;
   let args = arguments;
 
   let counter = 3;
-  for (let key in sandbox.extensions) {
+  for (let key of Object.keys(_state.extensions)) {
     counter += 2;
-    extensions.run(sandbox.extensions[key], function(err, fault, res) {
+    extensions.run(_state.extensions[key], function(err, fault, res) {
       if (err || fault) {
         if (counter & 1)
           callback(err, fault);
         return counter = 0;
       }
-      extCache[key] = res;
+      _state.sessionContext.extensionsCache[key] = res;
       if ((counter -= 2) === 1)
         if (status === 2)
           return run.apply(null, args);
         else
-          return callback(null, null, clr, decs, status === 0, ret);
+          return callback(null, null, _state.clear, _state.declarations, status === 0, ret);
     });
   }
 
@@ -306,7 +291,7 @@ function run(script, globals, timestamp, deviceData, extensionsCache, startRevis
     if (status === 2)
       return run.apply(null, args);
     else
-      return callback(null, null, clr, decs, status === 0, ret);
+      return callback(null, null, _state.clear, _state.declarations, status === 0, ret);
 }
 
 
diff --git a/lib/session.coffee b/lib/session.coffee
index 9f56ecf..96e3ecd 100644
--- a/lib/session.coffee
+++ b/lib/session.coffee
@@ -348,8 +348,7 @@ runProvisions = (sessionContext, provisions, startRevision, endRevision, callbac
 
     counter += 2
     sandbox.run(allProvisions[provision[0]].script,
-      {args: provision.slice(1)}, sessionContext.timestamp, sessionContext.deviceData,
-      sessionContext.extensionsCache, startRevision, endRevision,
+      {args: provision.slice(1)}, sessionContext, startRevision, endRevision,
       (err, _fault, _clear, _declarations, _done) ->
         if err or _fault
           callback(err, _fault) if counter & 1
@@ -357,10 +356,10 @@ runProvisions = (sessionContext, provisions, startRevision, endRevision, callbac
 
         done &&= _done
 
-        if _declarations
+        if _declarations.length
           allDeclarations = allDeclarations.concat(_declarations)
 
-        if _clear
+        if _clear.length
           allClear = allClear.concat(_clear)
 
         if (counter -= 2) == 1
@@ -382,8 +381,7 @@ runVirtualParameters = (sessionContext, provisions, startRevision, endRevision,
     counter += 2
     globals = {TIMESTAMPS: provision[1], VALUES: provision[2]}
     sandbox.run(allVirtualParameters[provision[0]].script, globals,
-      sessionContext.timestamp, sessionContext.deviceData,
-      sessionContext.extensionsCache, startRevision, endRevision,
+      sessionContext, startRevision, endRevision,
       (err, _fault, _clear, _declarations, _done, _returnValue) ->
         if err or _fault
           callback(err, _fault) if counter & 1
@@ -391,10 +389,10 @@ runVirtualParameters = (sessionContext, provisions, startRevision, endRevision,
 
         done &&= _done
 
-        if _declarations
+        if _declarations.length
           allDeclarations = allDeclarations.concat(_declarations)
 
-        if _clear
+        if _clear.length
           allClear = allClear.concat(_clear)
 
         if _done
@@ -575,7 +573,7 @@ rpcRequest = (sessionContext, _declarations, callback) ->
         return callback(null, fault)
 
       sessionContext.declarations.push(decs)
-      sessionContext.doneProvisions |= 1 << inception if done or not decs.length
+      sessionContext.doneProvisions |= 1 << inception if done
 
       for d in decs
         for ad in device.getAliasDeclarations(d[0], 1)