diff --git a/src/apex/apex.ts b/src/apex/apex.ts
index c02eddd9..a152ca5f 100644
--- a/src/apex/apex.ts
+++ b/src/apex/apex.ts
@@ -189,9 +189,9 @@ const keywords = [
 
 // create case variations of the keywords - apex is case insensitive, but we can't make the highlighter case insensitive
 // because we use a heuristic to assume that identifiers starting with an upper case letter are types.
-const uppercaseFirstLetter = (lowercase) => lowercase.charAt(0).toUpperCase() + lowercase.substr(1);
+const uppercaseFirstLetter = (lowercase: string) => lowercase.charAt(0).toUpperCase() + lowercase.substr(1);
 
-let keywordsWithCaseVariations = [];
+let keywordsWithCaseVariations: string[] = [];
 keywords.forEach(lowercase => {
 	keywordsWithCaseVariations.push(lowercase);
 	keywordsWithCaseVariations.push(lowercase.toUpperCase());
diff --git a/src/mocha.d.ts b/src/mocha.d.ts
index a86e7e70..803376f2 100644
--- a/src/mocha.d.ts
+++ b/src/mocha.d.ts
@@ -5,9 +5,9 @@
 
 declare function run(): void;
 
-declare function suite(name: string, fn: (err?)=>void);
-declare function test(name: string, fn: (done?: (err?)=>void)=>void);
-declare function suiteSetup(fn: (done?: (err?)=>void)=>void);
-declare function suiteTeardown(fn: (done?: (err?)=>void)=>void);
-declare function setup(fn: (done?: (err?)=>void)=>void);
-declare function teardown(fn: (done?: (err?)=>void)=>void);
+declare function suite(name: string, fn: (err?: any)=>void): void;
+declare function test(name: string, fn: (done: (err?: any)=>void)=>void): void;
+declare function suiteSetup(fn: (done: (err?: any)=>void)=>void): void;
+declare function suiteTeardown(fn: (done: (err?: any)=>void)=>void): void;
+declare function setup(fn: (done: (err?: any)=>void)=>void): void;
+declare function teardown(fn: (done: (err?: any)=>void)=>void): void;
diff --git a/src/tsconfig.json b/src/tsconfig.json
index ce5a8cde..09e1d4d8 100644
--- a/src/tsconfig.json
+++ b/src/tsconfig.json
@@ -3,6 +3,7 @@
     "module": "amd",
     "outDir": "../release/dev",
     "target": "es5",
+	"strict": true,
     "lib": [
       "dom",
       "es5",