diff --git a/gulp-istanbul/gulp-istanbul-tests.ts b/gulp-istanbul/gulp-istanbul-tests.ts
index 0d64b53d0..aada03de1 100644
--- a/gulp-istanbul/gulp-istanbul-tests.ts
+++ b/gulp-istanbul/gulp-istanbul-tests.ts
@@ -7,7 +7,7 @@ function testFramework(): NodeJS.ReadWriteStream {
     return null;
 }
 
-gulp.task('test', function (cb) {
+gulp.task('test', function (cb: Function) {
     gulp.src(['lib/**/*.js', 'main.js'])
         .pipe(istanbul()) // Covering files
         .pipe(gulp.dest('test-tmp/'))
@@ -19,7 +19,7 @@ gulp.task('test', function (cb) {
         });
 });
 
-gulp.task('test', function (cb) {
+gulp.task('test', function (cb: Function) {
     gulp.src(['lib/**/*.js', 'main.js'])
         .pipe(istanbul({includeUntested: true})) // Covering files
         .pipe(istanbul.hookRequire())
@@ -31,7 +31,7 @@ gulp.task('test', function (cb) {
         });
 });
 
-gulp.task('test', function (cb) {
+gulp.task('test', function (cb: Function) {
     gulp.src(['lib/**/*.js', 'main.js'])
         .pipe(istanbul({includeUntested: true})) // Covering files
         .pipe(istanbul.hookRequire())
@@ -42,4 +42,4 @@ gulp.task('test', function (cb) {
                 .pipe(istanbul.enforceThresholds({ thresholds: { global: 90 } })) //
                 .on('end', cb);
         });
-});
\ No newline at end of file
+});
diff --git a/gulp-watch/gulp-watch-tests.ts b/gulp-watch/gulp-watch-tests.ts
index 9d9303ac2..dd237dccc 100644
--- a/gulp-watch/gulp-watch-tests.ts
+++ b/gulp-watch/gulp-watch-tests.ts
@@ -10,7 +10,7 @@ gulp.task('stream', () =>
         .pipe(gulp.dest('build'))
 );
 
-gulp.task('callback', (cb) =>
+gulp.task('callback', (cb: Function) =>
     watch('css/**/*.css', () =>
         gulp.src('css/**/*.css')
             .pipe(watch('css/**/*.css'))