diff --git a/package-lock.json b/package-lock.json
index 3e84db9..095a735 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "simple-mapper",
-  "version": "2.1.4",
+  "version": "2.2.0",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -352,6 +352,7 @@
       "resolved": "https://registry.npmjs.org/align-text/-/align-text-0.1.4.tgz",
       "integrity": "sha1-DNkKVhCT810KmSVsIrcGlDP60Rc=",
       "dev": true,
+      "optional": true,
       "requires": {
         "kind-of": "3.2.2",
         "longest": "1.0.1",
@@ -363,6 +364,7 @@
           "resolved": "https://registry.npmjs.org/kind-of/-/kind-of-3.2.2.tgz",
           "integrity": "sha1-MeohpzS6ubuw8yRm2JOupR5KPGQ=",
           "dev": true,
+          "optional": true,
           "requires": {
             "is-buffer": "1.1.6"
           }
@@ -1448,13 +1450,31 @@
       }
     },
     "cross-env": {
-      "version": "5.1.5",
-      "resolved": "https://registry.npmjs.org/cross-env/-/cross-env-5.1.5.tgz",
-      "integrity": "sha512-GSiNTbvTU3pXzewRKGP0Y+rVP2CzifY2pqSEdtHzLLj41pRdkrgY7e4uSnBoR/pmYaqZr/lwwjg/Q4kNX30hWQ==",
+      "version": "6.0.0",
+      "resolved": "https://registry.npmjs.org/cross-env/-/cross-env-6.0.0.tgz",
+      "integrity": "sha512-G/B6gtkjgthT8AP/xN1wdj5Xe18fVyk58JepK8GxpUbqcz3hyWxegocMbvnZK+KoTslwd0ACZ3woi/DVUdVjyQ==",
       "dev": true,
       "requires": {
-        "cross-spawn": "5.1.0",
-        "is-windows": "1.0.2"
+        "cross-spawn": "^7.0.0"
+      },
+      "dependencies": {
+        "cross-spawn": {
+          "version": "7.0.0",
+          "resolved": "https://registry.npmjs.org/cross-spawn/-/cross-spawn-7.0.0.tgz",
+          "integrity": "sha512-6U/8SMK2FBNnB21oQ4+6Nsodxanw1gTkntYA2zBdkFYFu3ZDx65P2ONEXGSvob/QS6REjVHQ9zxzdOafwFdstw==",
+          "dev": true,
+          "requires": {
+            "path-key": "^3.1.0",
+            "shebang-command": "^1.2.0",
+            "which": "^1.2.9"
+          }
+        },
+        "path-key": {
+          "version": "3.1.0",
+          "resolved": "https://registry.npmjs.org/path-key/-/path-key-3.1.0.tgz",
+          "integrity": "sha512-8cChqz0RP6SHJkMt48FW0A7+qUOn+OsnOsVtzI59tZ8m+5bCSk7hzwET0pulwOM2YMn9J1efb07KB9l9f30SGg==",
+          "dev": true
+        }
       }
     },
     "cross-spawn": {
@@ -2432,7 +2452,8 @@
         "ansi-regex": {
           "version": "2.1.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "aproba": {
           "version": "1.1.1",
@@ -2483,7 +2504,8 @@
         "balanced-match": {
           "version": "0.4.2",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "bcrypt-pbkdf": {
           "version": "1.0.1",
@@ -2498,6 +2520,7 @@
           "version": "0.0.9",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "inherits": "2.0.3"
           }
@@ -2506,6 +2529,7 @@
           "version": "2.10.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "hoek": "2.16.3"
           }
@@ -2514,6 +2538,7 @@
           "version": "1.1.7",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "balanced-match": "0.4.2",
             "concat-map": "0.0.1"
@@ -2522,7 +2547,8 @@
         "buffer-shims": {
           "version": "1.0.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "caseless": {
           "version": "0.12.0",
@@ -2539,12 +2565,14 @@
         "code-point-at": {
           "version": "1.1.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "combined-stream": {
           "version": "1.0.5",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "delayed-stream": "1.0.0"
           }
@@ -2552,22 +2580,26 @@
         "concat-map": {
           "version": "0.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "console-control-strings": {
           "version": "1.1.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "core-util-is": {
           "version": "1.0.2",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "cryptiles": {
           "version": "2.0.5",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "boom": "2.10.1"
           }
@@ -2607,7 +2639,8 @@
         "delayed-stream": {
           "version": "1.0.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "delegates": {
           "version": "1.0.0",
@@ -2639,7 +2672,8 @@
         "extsprintf": {
           "version": "1.0.2",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "forever-agent": {
           "version": "0.6.1",
@@ -2661,12 +2695,14 @@
         "fs.realpath": {
           "version": "1.0.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "fstream": {
           "version": "1.0.11",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "graceful-fs": "4.1.11",
             "inherits": "2.0.3",
@@ -2722,6 +2758,7 @@
           "version": "7.1.2",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "fs.realpath": "1.0.0",
             "inflight": "1.0.6",
@@ -2734,7 +2771,8 @@
         "graceful-fs": {
           "version": "4.1.11",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "har-schema": {
           "version": "1.0.5",
@@ -2762,6 +2800,7 @@
           "version": "3.1.3",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "boom": "2.10.1",
             "cryptiles": "2.0.5",
@@ -2772,7 +2811,8 @@
         "hoek": {
           "version": "2.16.3",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "http-signature": {
           "version": "1.1.1",
@@ -2789,6 +2829,7 @@
           "version": "1.0.6",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "once": "1.4.0",
             "wrappy": "1.0.2"
@@ -2797,7 +2838,8 @@
         "inherits": {
           "version": "2.0.3",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "ini": {
           "version": "1.3.4",
@@ -2809,6 +2851,7 @@
           "version": "1.0.0",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "number-is-nan": "1.0.1"
           }
@@ -2822,7 +2865,8 @@
         "isarray": {
           "version": "1.0.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "isstream": {
           "version": "0.1.2",
@@ -2895,12 +2939,14 @@
         "mime-db": {
           "version": "1.27.0",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "mime-types": {
           "version": "2.1.15",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "mime-db": "1.27.0"
           }
@@ -2909,6 +2955,7 @@
           "version": "3.0.4",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "brace-expansion": "1.1.7"
           }
@@ -2916,12 +2963,14 @@
         "minimist": {
           "version": "0.0.8",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "mkdirp": {
           "version": "0.5.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "minimist": "0.0.8"
           }
@@ -2976,7 +3025,8 @@
         "number-is-nan": {
           "version": "1.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "oauth-sign": {
           "version": "0.8.2",
@@ -2994,6 +3044,7 @@
           "version": "1.4.0",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "wrappy": "1.0.2"
           }
@@ -3023,7 +3074,8 @@
         "path-is-absolute": {
           "version": "1.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "performance-now": {
           "version": "0.2.0",
@@ -3034,7 +3086,8 @@
         "process-nextick-args": {
           "version": "1.0.7",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "punycode": {
           "version": "1.4.1",
@@ -3072,6 +3125,7 @@
           "version": "2.2.9",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "buffer-shims": "1.0.0",
             "core-util-is": "1.0.2",
@@ -3116,6 +3170,7 @@
           "version": "2.6.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "glob": "7.1.2"
           }
@@ -3123,7 +3178,8 @@
         "safe-buffer": {
           "version": "5.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "semver": {
           "version": "5.3.0",
@@ -3147,6 +3203,7 @@
           "version": "1.0.9",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "hoek": "2.16.3"
           }
@@ -3180,6 +3237,7 @@
           "version": "1.0.2",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "code-point-at": "1.1.0",
             "is-fullwidth-code-point": "1.0.0",
@@ -3190,6 +3248,7 @@
           "version": "1.0.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "safe-buffer": "5.0.1"
           }
@@ -3204,6 +3263,7 @@
           "version": "3.0.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "ansi-regex": "2.1.1"
           }
@@ -3218,6 +3278,7 @@
           "version": "2.2.1",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "block-stream": "0.0.9",
             "fstream": "1.0.11",
@@ -3273,7 +3334,8 @@
         "util-deprecate": {
           "version": "1.0.2",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "uuid": {
           "version": "3.0.1",
@@ -3302,7 +3364,8 @@
         "wrappy": {
           "version": "1.0.2",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         }
       }
     },
@@ -3402,7 +3465,8 @@
       }
     },
     "graceful-fs": {
-      "version": "https://registry.npmjs.org/graceful-fs/-/graceful-fs-4.1.11.tgz",
+      "version": "4.1.11",
+      "resolved": "https://registry.npmjs.org/graceful-fs/-/graceful-fs-4.1.11.tgz",
       "integrity": "sha1-Dovf5NHduIVNZOBOp8AOKgJuVlg=",
       "dev": true
     },
@@ -4356,7 +4420,8 @@
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/longest/-/longest-1.0.1.tgz",
       "integrity": "sha1-MKCy2jj3N3DoKUoNIuZiXtd9AJc=",
-      "dev": true
+      "dev": true,
+      "optional": true
     },
     "lru-cache": {
       "version": "4.1.3",
@@ -4976,6 +5041,7 @@
           "version": "0.1.4",
           "bundled": true,
           "dev": true,
+          "optional": true,
           "requires": {
             "kind-of": "3.2.2",
             "longest": "1.0.1",
@@ -6006,7 +6072,8 @@
         "longest": {
           "version": "1.0.1",
           "bundled": true,
-          "dev": true
+          "dev": true,
+          "optional": true
         },
         "loose-envify": {
           "version": "1.3.1",
@@ -7961,7 +8028,7 @@
           "integrity": "sha1-gXDBRE1wOOCMrqBaN0+uL6NJ4Vw=",
           "dev": true,
           "requires": {
-            "graceful-fs": "https://registry.npmjs.org/graceful-fs/-/graceful-fs-4.1.11.tgz"
+            "graceful-fs": "4.1.11"
           }
         },
         "taskgroup": {
diff --git a/package.json b/package.json
index b69c1e0..d5b8259 100644
--- a/package.json
+++ b/package.json
@@ -43,7 +43,7 @@
     "alsatian-fluent-assertions": "^1.0.0-alpha018",
     "codecov": "^3.0.0",
     "core-js": "^2.5.6",
-    "cross-env": "^5.1.5",
+    "cross-env": "^6.0.0",
     "npm-run-all": "^4.1.3",
     "nyc": "^12.0.1",
     "rxjs": "^5.5.10",