diff --git a/.travis.yml b/.travis.yml
index 03d903ee3..db97ea17c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -6,7 +6,7 @@ script:
   - npm run buildAndTest
 
 node_js:
-  - "6"
+  - "8"
   - "stable"
 
 cache:
diff --git a/package-lock.json b/package-lock.json
index 6bbe356ec..ef3306859 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,13 +1,13 @@
 {
   "name": "sip.js",
-  "version": "0.13.0",
+  "version": "0.13.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
     "@types/node": {
-      "version": "10.12.20",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-10.12.20.tgz",
-      "integrity": "sha512-9spv6SklidqxevvZyOUGjZVz4QRXGu2dNaLyXIFzFYZW0AGDykzPRIUFJXTlQXyfzAucddwTcGtJNim8zqSOPA==",
+      "version": "10.12.21",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-10.12.21.tgz",
+      "integrity": "sha512-CBgLNk4o3XMnqMc0rhb6lc77IwShMEglz05deDcn2lQxyXEZivfwgYJu7SMha9V5XcrP6qZuevTHV/QrN2vjKQ==",
       "dev": true
     },
     "@webassemblyjs/ast": {
@@ -205,9 +205,9 @@
       }
     },
     "acorn": {
-      "version": "6.0.6",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.0.6.tgz",
-      "integrity": "sha512-5M3G/A4uBSMIlfJ+h9W125vJvPFH/zirISsW5qfxF5YzEvXJCtolLoQvM5yZft0DvMcUrPGKPOlgEu55I6iUtA==",
+      "version": "6.0.7",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-6.0.7.tgz",
+      "integrity": "sha512-HNJNgE60C9eOTgn974Tlp3dpLZdUr+SoxxDwPaY9J/kDNOLQTkaDgwBUXAF4SSsrAwD9RpdxuHK/EbuF+W9Ahw==",
       "dev": true
     },
     "acorn-dynamic-import": {
@@ -223,9 +223,9 @@
       "dev": true
     },
     "ajv": {
-      "version": "6.7.0",
-      "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.7.0.tgz",
-      "integrity": "sha512-RZXPviBTtfmtka9n9sy1N5M5b82CbxWIR6HIis4s3WQTXDJamc/0gpCWNGz6EWdWp4DOfjzJfhz/AS9zVPjjWg==",
+      "version": "6.8.1",
+      "resolved": "https://registry.npmjs.org/ajv/-/ajv-6.8.1.tgz",
+      "integrity": "sha512-eqxCp82P+JfqL683wwsL73XmFs1eG6qjw+RD3YHx+Jll1r0jNd4dh8QG9NYAeNGA/hnZjeEDgtTskgJULbxpWQ==",
       "dev": true,
       "requires": {
         "fast-deep-equal": "^2.0.1",
@@ -1369,9 +1369,9 @@
       "dev": true
     },
     "duplexify": {
-      "version": "3.6.1",
-      "resolved": "https://registry.npmjs.org/duplexify/-/duplexify-3.6.1.tgz",
-      "integrity": "sha512-vM58DwdnKmty+FSPzT14K9JXb90H+j5emaR4KYbr2KTIz00WHGbWOe5ghQTx233ZCLZtrGDALzKwcjEtSt35mA==",
+      "version": "3.7.1",
+      "resolved": "https://registry.npmjs.org/duplexify/-/duplexify-3.7.1.tgz",
+      "integrity": "sha512-07z8uv2wMyS51kKhD1KsdXJg5WQ6t93RneqRxUHnskXVtlYYkLqM0gqStQZ3pj073g687jPCHrqNfCzawLYh5g==",
       "dev": true,
       "requires": {
         "end-of-stream": "^1.0.0",
@@ -1936,13 +1936,26 @@
       "dev": true
     },
     "flush-write-stream": {
-      "version": "1.0.3",
-      "resolved": "https://registry.npmjs.org/flush-write-stream/-/flush-write-stream-1.0.3.tgz",
-      "integrity": "sha512-calZMC10u0FMUqoiunI2AiGIIUtUIvifNwkHhNupZH4cbNnW1Itkoh/Nf5HFYmDrwWPjrUxpkZT0KhuCq0jmGw==",
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/flush-write-stream/-/flush-write-stream-1.1.0.tgz",
+      "integrity": "sha512-6MHED/cmsyux1G4/Cek2Z776y9t7WCNd3h2h/HW91vFeU7pzMhA8XvAlDhHcanG5IWuIh/xcC7JASY4WQpG6xg==",
       "dev": true,
       "requires": {
-        "inherits": "^2.0.1",
-        "readable-stream": "^2.0.4"
+        "inherits": "^2.0.3",
+        "readable-stream": "^3.1.1"
+      },
+      "dependencies": {
+        "readable-stream": {
+          "version": "3.1.1",
+          "resolved": "https://registry.npmjs.org/readable-stream/-/readable-stream-3.1.1.tgz",
+          "integrity": "sha512-DkN66hPyqDhnIQ6Jcsvx9bFjhw214O4poMBcIMgPVpQvNy9a0e0Uhg5SqySyDKAmUlwt8LonTBz1ezOnM8pUdA==",
+          "dev": true,
+          "requires": {
+            "inherits": "^2.0.3",
+            "string_decoder": "^1.1.1",
+            "util-deprecate": "^1.0.1"
+          }
+        }
       }
     },
     "follow-redirects": {
@@ -2619,12 +2632,6 @@
         "resolve-dir": "^1.0.0"
       }
     },
-    "global-modules-path": {
-      "version": "2.3.1",
-      "resolved": "https://registry.npmjs.org/global-modules-path/-/global-modules-path-2.3.1.tgz",
-      "integrity": "sha512-y+shkf4InI7mPRHSo2b/k6ix6+NLDtyccYv86whhxrSGX9wjPX1VMITmrDbE1eh7zkzhiWtW2sHklJYoQ62Cxg==",
-      "dev": true
-    },
     "global-prefix": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/global-prefix/-/global-prefix-1.0.2.tgz",
@@ -3084,9 +3091,9 @@
       "dev": true
     },
     "karma": {
-      "version": "3.1.4",
-      "resolved": "https://registry.npmjs.org/karma/-/karma-3.1.4.tgz",
-      "integrity": "sha512-31Vo8Qr5glN+dZEVIpnPCxEGleqE0EY6CtC2X9TagRV3rRQ3SNrvfhddICkJgUK3AgqpeKSZau03QumTGhGoSw==",
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/karma/-/karma-4.0.0.tgz",
+      "integrity": "sha512-EFoFs3F6G0BcUGPNOn/YloGOb3h09hzTguyXlg6loHlKY76qbJikkcyPk43m2kfRF65TUGda/mig29QQtyhm1g==",
       "dev": true,
       "requires": {
         "bluebird": "^3.3.0",
@@ -3201,12 +3208,6 @@
         "invert-kv": "^2.0.0"
       }
     },
-    "lightercollective": {
-      "version": "0.1.0",
-      "resolved": "https://registry.npmjs.org/lightercollective/-/lightercollective-0.1.0.tgz",
-      "integrity": "sha512-J9tg5uraYoQKaWbmrzDDexbG6hHnMcWS1qLYgJSWE+mpA3U5OCSeMUhb+K55otgZJ34oFdR0ECvdIb3xuO5JOQ==",
-      "dev": true
-    },
     "loader-runner": {
       "version": "2.4.0",
       "resolved": "https://registry.npmjs.org/loader-runner/-/loader-runner-2.4.0.tgz",
@@ -3366,14 +3367,14 @@
       "dev": true
     },
     "mem": {
-      "version": "4.0.0",
-      "resolved": "https://registry.npmjs.org/mem/-/mem-4.0.0.tgz",
-      "integrity": "sha512-WQxG/5xYc3tMbYLXoXPm81ET2WDULiU5FxbuIoNbJqLOOI8zehXFdZuiUEgfdrU2mVB1pxBZUGlYORSrpuJreA==",
+      "version": "4.1.0",
+      "resolved": "https://registry.npmjs.org/mem/-/mem-4.1.0.tgz",
+      "integrity": "sha512-I5u6Q1x7wxO0kdOpYBB28xueHADYps5uty/zg936CiG8NTe5sJL8EjrCuLneuDW3PlMdZBGDIn8BirEVdovZvg==",
       "dev": true,
       "requires": {
         "map-age-cleaner": "^0.1.1",
         "mimic-fn": "^1.0.0",
-        "p-is-promise": "^1.1.0"
+        "p-is-promise": "^2.0.0"
       }
     },
     "memory-fs": {
@@ -3795,9 +3796,9 @@
       "dev": true
     },
     "p-is-promise": {
-      "version": "1.1.0",
-      "resolved": "http://registry.npmjs.org/p-is-promise/-/p-is-promise-1.1.0.tgz",
-      "integrity": "sha1-nJRWmJ6fZYgBewQ01WCXZ1w9oF4=",
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/p-is-promise/-/p-is-promise-2.0.0.tgz",
+      "integrity": "sha512-pzQPhYMCAgLAKPWD2jC3Se9fEfrD9npNos0y150EeqZll7akhEgGhTW/slB6lHku8AvYGiJ+YJ5hfHKePPgFWg==",
       "dev": true
     },
     "p-limit": {
@@ -4801,14 +4802,14 @@
       "dev": true
     },
     "terser": {
-      "version": "3.14.1",
-      "resolved": "https://registry.npmjs.org/terser/-/terser-3.14.1.tgz",
-      "integrity": "sha512-NSo3E99QDbYSMeJaEk9YW2lTg3qS9V0aKGlb+PlOrei1X02r1wSBHCNX/O+yeTRFSWPKPIGj6MqvvdqV4rnVGw==",
+      "version": "3.16.1",
+      "resolved": "https://registry.npmjs.org/terser/-/terser-3.16.1.tgz",
+      "integrity": "sha512-JDJjgleBROeek2iBcSNzOHLKsB/MdDf+E/BOAJ0Tk9r7p9/fVobfv7LMJ/g/k3v9SXdmjZnIlFd5nfn/Rt0Xow==",
       "dev": true,
       "requires": {
         "commander": "~2.17.1",
         "source-map": "~0.6.1",
-        "source-map-support": "~0.5.6"
+        "source-map-support": "~0.5.9"
       },
       "dependencies": {
         "commander": {
@@ -4826,9 +4827,9 @@
       }
     },
     "terser-webpack-plugin": {
-      "version": "1.2.1",
-      "resolved": "https://registry.npmjs.org/terser-webpack-plugin/-/terser-webpack-plugin-1.2.1.tgz",
-      "integrity": "sha512-GGSt+gbT0oKcMDmPx4SRSfJPE1XaN3kQRWG4ghxKQw9cn5G9x6aCKSsgYdvyM0na9NJ4Drv0RG6jbBByZ5CMjw==",
+      "version": "1.2.2",
+      "resolved": "https://registry.npmjs.org/terser-webpack-plugin/-/terser-webpack-plugin-1.2.2.tgz",
+      "integrity": "sha512-1DMkTk286BzmfylAvLXwpJrI7dWa5BnFmscV/2dCr8+c56egFcbaeFAl7+sujAjdmpLam21XRdhA4oifLyiWWg==",
       "dev": true,
       "requires": {
         "cacache": "^11.0.2",
@@ -4836,7 +4837,7 @@
         "schema-utils": "^1.0.0",
         "serialize-javascript": "^1.4.0",
         "source-map": "^0.6.1",
-        "terser": "^3.8.1",
+        "terser": "^3.16.1",
         "webpack-sources": "^1.1.0",
         "worker-farm": "^1.5.2"
       },
@@ -5022,9 +5023,9 @@
       "dev": true
     },
     "typescript": {
-      "version": "3.2.4",
-      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.2.4.tgz",
-      "integrity": "sha512-0RNDbSdEokBeEAkgNbxJ+BLwSManFy9TeXz8uW+48j/xhEXv1ePME60olyzw2XzUqUBNAYFeJadIqAgNqIACwg==",
+      "version": "3.3.1",
+      "resolved": "https://registry.npmjs.org/typescript/-/typescript-3.3.1.tgz",
+      "integrity": "sha512-cTmIDFW7O0IHbn1DPYjkiebHxwtCMU+eTy30ZtJNBPF9j2O1ITu5XH2YnBeVRKWHqF+3JQwWJv0Q0aUgX8W7IA==",
       "dev": true
     },
     "ultron": {
@@ -5253,9 +5254,9 @@
       }
     },
     "webpack": {
-      "version": "4.29.0",
-      "resolved": "https://registry.npmjs.org/webpack/-/webpack-4.29.0.tgz",
-      "integrity": "sha512-pxdGG0keDBtamE1mNvT5zyBdx+7wkh6mh7uzMOo/uRQ/fhsdj5FXkh/j5mapzs060forql1oXqXN9HJGju+y7w==",
+      "version": "4.29.1",
+      "resolved": "https://registry.npmjs.org/webpack/-/webpack-4.29.1.tgz",
+      "integrity": "sha512-dY3KyQIVeg6cDPj9G5Bnjy9Pt9SoCpbNWl0RDKHstbd3MWe0dG9ri4RQRpCm43iToy3zoA1IMOpFkJ8Clnc7FQ==",
       "dev": true,
       "requires": {
         "@webassemblyjs/ast": "1.7.11",
@@ -5285,9 +5286,9 @@
       }
     },
     "webpack-cli": {
-      "version": "3.2.1",
-      "resolved": "https://registry.npmjs.org/webpack-cli/-/webpack-cli-3.2.1.tgz",
-      "integrity": "sha512-jeJveHwz/vwpJ3B8bxEL5a/rVKIpRNJDsKggfKnxuYeohNDW4Y/wB9N/XHJA093qZyS0r6mYL+/crLsIol4WKA==",
+      "version": "3.2.3",
+      "resolved": "https://registry.npmjs.org/webpack-cli/-/webpack-cli-3.2.3.tgz",
+      "integrity": "sha512-Ik3SjV6uJtWIAN5jp5ZuBMWEAaP5E4V78XJ2nI+paFPh8v4HPSwo/myN0r29Xc/6ZKnd2IdrAlpSgNOu2CDQ6Q==",
       "dev": true,
       "requires": {
         "chalk": "^2.4.1",
@@ -5295,10 +5296,8 @@
         "enhanced-resolve": "^4.1.0",
         "findup-sync": "^2.0.0",
         "global-modules": "^1.0.0",
-        "global-modules-path": "^2.3.0",
         "import-local": "^2.0.0",
         "interpret": "^1.1.0",
-        "lightercollective": "^0.1.0",
         "loader-utils": "^1.1.0",
         "supports-color": "^5.5.0",
         "v8-compile-cache": "^2.0.2",
diff --git a/package.json b/package.json
index 656c23083..0ef58d38b 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "sip.js",
   "title": "SIP.js",
   "description": "A simple, intuitive, and powerful JavaScript signaling library",
-  "version": "0.13.0",
+  "version": "0.13.1",
   "license": "MIT",
   "main": "lib/index.js",
   "homepage": "https://sipjs.com",
@@ -27,10 +27,10 @@
     "crypto-js": "^3.1.9-1"
   },
   "devDependencies": {
-    "@types/node": "^10.12.20",
+    "@types/node": "^10.12.21",
     "circular-dependency-plugin": "^5.0.2",
     "jasmine-core": "^3.3.0",
-    "karma": "^3.1.4",
+    "karma": "^4.0.0",
     "karma-chrome-launcher": "^2.2.0",
     "karma-cli": "^2.0.0",
     "karma-jasmine": "^2.0.1",
@@ -41,12 +41,12 @@
     "ts-loader": "^5.3.3",
     "ts-pegjs": "0.2.2",
     "tslint": "^5.12.1",
-    "typescript": "^3.2.4",
-    "webpack": "^4.29.0",
-    "webpack-cli": "^3.2.1"
+    "typescript": "^3.3.1",
+    "webpack": "^4.29.1",
+    "webpack-cli": "^3.2.3"
   },
   "engines": {
-    "node": ">=6.0"
+    "node": ">=8.0"
   },
   "scripts": {
     "prebuild": "tslint -p tsconfig.json -c tslint.json",
diff --git a/src/UA.ts b/src/UA.ts
index a0b2c7597..bfb5f7dfd 100644
--- a/src/UA.ts
+++ b/src/UA.ts
@@ -479,7 +479,7 @@ export class UA extends EventEmitter implements UADefinition {
       // unload is not available in packaged apps
       if (!((global as any).chrome && (global as any).chrome.app && (global as any).chrome.app.runtime)) {
         this.environListener = this.stop;
-        environment.addEventListener("unload", this.environListener);
+        environment.addEventListener("unload", this.environListener.bind(this));
       }
     }