diff --git a/package.json b/package.json
index 6c7eb7a..f332b18 100644
--- a/package.json
+++ b/package.json
@@ -61,9 +61,9 @@
 		"lodash.isequal": "^4.5.0",
 		"nyc": "^11.2.1",
 		"tslint": "^5.9.1",
-		"tslint-xo": "^0.5.0",
+		"tslint-xo": "^0.6.0",
 		"typedoc": "^0.9.0",
-		"typescript": "^2.6.2",
+		"typescript": "^2.7.0",
 		"vali-date": "^1.0.0",
 		"webpack": "^3.8.1"
 	},
diff --git a/source/lib/predicates/array.ts b/source/lib/predicates/array.ts
index 6ddac5f..862c7dc 100644
--- a/source/lib/predicates/array.ts
+++ b/source/lib/predicates/array.ts
@@ -1,4 +1,4 @@
-import isEqual = require('lodash.isequal');				// tslint:disable-line:no-require-imports
+import isEqual = require('lodash.isequal'); // tslint:disable-line:no-require-imports
 import ow from '../..';
 import {Predicate, Context} from './predicate';
 
diff --git a/source/lib/predicates/map.ts b/source/lib/predicates/map.ts
index 499a413..6e25200 100644
--- a/source/lib/predicates/map.ts
+++ b/source/lib/predicates/map.ts
@@ -1,4 +1,4 @@
-import isEqual = require('lodash.isequal');				// tslint:disable-line:no-require-imports
+import isEqual = require('lodash.isequal'); // tslint:disable-line:no-require-imports
 import {Predicate, Context} from './predicate';
 import hasItems from '../utils/has-items';
 import ofType from '../utils/of-type';
diff --git a/source/lib/predicates/set.ts b/source/lib/predicates/set.ts
index 43e7a5b..b54108d 100644
--- a/source/lib/predicates/set.ts
+++ b/source/lib/predicates/set.ts
@@ -1,4 +1,4 @@
-import isEqual = require('lodash.isequal');				// tslint:disable-line:no-require-imports
+import isEqual = require('lodash.isequal'); // tslint:disable-line:no-require-imports
 import {Predicate, Context} from './predicate';
 import hasItems from '../utils/has-items';
 import ofType from '../utils/of-type';
diff --git a/tsconfig.json b/tsconfig.json
index bfe4660..3c3681e 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -19,6 +19,7 @@
 		"noFallthroughCasesInSwitch": true,
 		"strictNullChecks": true,
 		"strictFunctionTypes": true,
+		"strictPropertyInitialization": true,
 		"alwaysStrict": true
 	},
 	"exclude": [