diff --git a/README.md b/README.md
index 78ae7453..1e9089e0 100644
--- a/README.md
+++ b/README.md
@@ -91,7 +91,7 @@ Add `gulp --completion=fish | source` to `~/.config/fish/config.fish`.
 
 ## Compilers
 
-You can find a list of supported languages at https://github.com/gulpjs/interpret. If you would like to add support for a new language, send pull requests/open issues on that project.
+You can find a list of supported JavaScript variant languages in [Interpret][interpret-js-variants]. If you would like to add support for a new language, send pull requests/open issues on that project.
 
 ## Environment
 
@@ -99,7 +99,7 @@ The CLI adds `process.env.INIT_CWD` which is the original cwd it was launched fr
 
 ## Configuration
 
-Configuration is supported through the use of a `.gulp.*` file (e.g. `.gulp.json`, `.gulp.yml`). You can find a list of supported languages at https://github.com/gulpjs/interpret.
+Configuration is supported through the use of a `.gulp.*` file (e.g. `.gulp.js`, `.gulp.ts`). You can find a list of supported JavaScript variant languages in [Interpret][interpret-js-variants].
 
 A configuration file from the current working directory (`cwd`) or above are selected before a configuration file from the home directory (`~`).
 
@@ -224,6 +224,9 @@ __Some flags only work with gulp 4 and will be ignored when invoked against gulp
 
 MIT
 
+<!-- prettier-ignore-start -->
+[interpret-js-variants]: https://github.com/gulpjs/interpret#jsvariants
+<!-- prettier-ignore-end -->
 
 <!-- prettier-ignore-start -->
 [downloads-image]: https://img.shields.io/npm/dm/gulp-cli.svg?style=flat-square
diff --git a/index.js b/index.js
index 2a2c7ad4..b0d50969 100644
--- a/index.js
+++ b/index.js
@@ -41,13 +41,13 @@ var cli = new Liftoff({
     {
       name: '.gulp',
       path: '.',
-      extensions: interpret.extensions,
+      extensions: interpret.jsVariants,
       findUp: true,
     },
     {
       name: '.gulp',
       path: '~',
-      extensions: interpret.extensions,
+      extensions: interpret.jsVariants,
     },
   ],
 });
diff --git a/test/fixtures/.gulp.js b/test/fixtures/.gulp.js
index 08a9d1e7..ad18e9c8 100644
--- a/test/fixtures/.gulp.js
+++ b/test/fixtures/.gulp.js
@@ -7,4 +7,4 @@ module.exports = {
       return "gulp-cli/test/fixtures";
     }
   }
-}
+};
diff --git a/test/fixtures/config/flags/continue/f/.gulp.js b/test/fixtures/config/flags/continue/f/.gulp.js
new file mode 100644
index 00000000..6edb0159
--- /dev/null
+++ b/test/fixtures/config/flags/continue/f/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    continue: false
+  }
+};
diff --git a/test/fixtures/config/flags/continue/f/.gulp.json b/test/fixtures/config/flags/continue/f/.gulp.json
deleted file mode 100644
index e0a7cbf2..00000000
--- a/test/fixtures/config/flags/continue/f/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "continue": false
-  }
-}
diff --git a/test/fixtures/config/flags/continue/t/.gulp.js b/test/fixtures/config/flags/continue/t/.gulp.js
new file mode 100644
index 00000000..ed371532
--- /dev/null
+++ b/test/fixtures/config/flags/continue/t/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    continue: true
+  }
+};
diff --git a/test/fixtures/config/flags/continue/t/.gulp.json b/test/fixtures/config/flags/continue/t/.gulp.json
deleted file mode 100644
index 7161f7a2..00000000
--- a/test/fixtures/config/flags/continue/t/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "continue": true
-  }
-}
diff --git a/test/fixtures/config/flags/gulpfile/autoload-fail/.gulp.js b/test/fixtures/config/flags/gulpfile/autoload-fail/.gulp.js
new file mode 100644
index 00000000..ecfc61d3
--- /dev/null
+++ b/test/fixtures/config/flags/gulpfile/autoload-fail/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  gulpfile: "./other_dir/gulpfile.coffee"
+};
diff --git a/test/fixtures/config/flags/gulpfile/autoload-fail/.gulp.json b/test/fixtures/config/flags/gulpfile/autoload-fail/.gulp.json
deleted file mode 100644
index 42846df5..00000000
--- a/test/fixtures/config/flags/gulpfile/autoload-fail/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "gulpfile": "./other_dir/gulpfile.coffee"
-}
diff --git a/test/fixtures/config/flags/gulpfile/autoload/.gulp.js b/test/fixtures/config/flags/gulpfile/autoload/.gulp.js
new file mode 100644
index 00000000..b307baf1
--- /dev/null
+++ b/test/fixtures/config/flags/gulpfile/autoload/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  gulpfile: "other_folder/gulpfile-exports.babel.js"
+};
diff --git a/test/fixtures/config/flags/gulpfile/autoload/.gulp.json b/test/fixtures/config/flags/gulpfile/autoload/.gulp.json
deleted file mode 100644
index 10c5b586..00000000
--- a/test/fixtures/config/flags/gulpfile/autoload/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "gulpfile": "other_folder/gulpfile-exports.babel.js"
-}
diff --git a/test/fixtures/config/flags/gulpfile/cwd/.gulp.js b/test/fixtures/config/flags/gulpfile/cwd/.gulp.js
new file mode 100644
index 00000000..3ff2eb25
--- /dev/null
+++ b/test/fixtures/config/flags/gulpfile/cwd/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  gulpfile: "../is/here/gulpfile-by-cwd-cfg.js"
+};
diff --git a/test/fixtures/config/flags/gulpfile/cwd/.gulp.json b/test/fixtures/config/flags/gulpfile/cwd/.gulp.json
deleted file mode 100644
index 7f0181dd..00000000
--- a/test/fixtures/config/flags/gulpfile/cwd/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "gulpfile": "../is/here/gulpfile-by-cwd-cfg.js"
-}
diff --git a/test/fixtures/config/flags/gulpfile/override-by-cliflag/.gulp.js b/test/fixtures/config/flags/gulpfile/override-by-cliflag/.gulp.js
new file mode 100644
index 00000000..3aa3b2db
--- /dev/null
+++ b/test/fixtures/config/flags/gulpfile/override-by-cliflag/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  gulpfile: "../cwd/gulpfile.js"
+};
diff --git a/test/fixtures/config/flags/gulpfile/override-by-cliflag/.gulp.json b/test/fixtures/config/flags/gulpfile/override-by-cliflag/.gulp.json
deleted file mode 100644
index fb737ede..00000000
--- a/test/fixtures/config/flags/gulpfile/override-by-cliflag/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "gulpfile": "../cwd/gulpfile.js"
-}
diff --git a/test/fixtures/config/flags/gulpfile/prj/.gulp.js b/test/fixtures/config/flags/gulpfile/prj/.gulp.js
new file mode 100644
index 00000000..321e3bdf
--- /dev/null
+++ b/test/fixtures/config/flags/gulpfile/prj/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  gulpfile: "../is/here/gulpfile-by-prj-cfg.js"
+};
diff --git a/test/fixtures/config/flags/gulpfile/prj/.gulp.json b/test/fixtures/config/flags/gulpfile/prj/.gulp.json
deleted file mode 100644
index 625bb7c1..00000000
--- a/test/fixtures/config/flags/gulpfile/prj/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "gulpfile": "../is/here/gulpfile-by-prj-cfg.js"
-}
diff --git a/test/fixtures/config/flags/logLevel/L/.gulp.js b/test/fixtures/config/flags/logLevel/L/.gulp.js
new file mode 100644
index 00000000..fca4e6b7
--- /dev/null
+++ b/test/fixtures/config/flags/logLevel/L/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    logLevel: 1
+  }
+}
diff --git a/test/fixtures/config/flags/logLevel/L/.gulp.json b/test/fixtures/config/flags/logLevel/L/.gulp.json
deleted file mode 100644
index 8b4448e9..00000000
--- a/test/fixtures/config/flags/logLevel/L/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "logLevel": 1
-  }
-}
diff --git a/test/fixtures/config/flags/logLevel/LL/.gulp.js b/test/fixtures/config/flags/logLevel/LL/.gulp.js
new file mode 100644
index 00000000..033e74d7
--- /dev/null
+++ b/test/fixtures/config/flags/logLevel/LL/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    logLevel: 2
+  }
+};
diff --git a/test/fixtures/config/flags/logLevel/LL/.gulp.json b/test/fixtures/config/flags/logLevel/LL/.gulp.json
deleted file mode 100644
index cd498c8d..00000000
--- a/test/fixtures/config/flags/logLevel/LL/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "logLevel": 2
-  }
-}
diff --git a/test/fixtures/config/flags/logLevel/LLL/.gulp.js b/test/fixtures/config/flags/logLevel/LLL/.gulp.js
new file mode 100644
index 00000000..5120f6f1
--- /dev/null
+++ b/test/fixtures/config/flags/logLevel/LLL/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    logLevel: 3
+  }
+};
diff --git a/test/fixtures/config/flags/logLevel/LLL/.gulp.json b/test/fixtures/config/flags/logLevel/LLL/.gulp.json
deleted file mode 100644
index 267a3cec..00000000
--- a/test/fixtures/config/flags/logLevel/LLL/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "logLevel": 3
-  }
-}
diff --git a/test/fixtures/config/flags/nodeFlags/array/.gulp.js b/test/fixtures/config/flags/nodeFlags/array/.gulp.js
new file mode 100644
index 00000000..29053b1a
--- /dev/null
+++ b/test/fixtures/config/flags/nodeFlags/array/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  nodeFlags: ["--lazy", "--trace-deprecation"]
+}
diff --git a/test/fixtures/config/flags/nodeFlags/array/.gulp.json b/test/fixtures/config/flags/nodeFlags/array/.gulp.json
deleted file mode 100644
index 79cd530d..00000000
--- a/test/fixtures/config/flags/nodeFlags/array/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "nodeFlags": ["--lazy", "--trace-deprecation"]
-}
diff --git a/test/fixtures/config/flags/preload/array/.gulp.json b/test/fixtures/config/flags/preload/array/.gulp.js
similarity index 56%
rename from test/fixtures/config/flags/preload/array/.gulp.json
rename to test/fixtures/config/flags/preload/array/.gulp.js
index 2f4855e1..da5c398f 100644
--- a/test/fixtures/config/flags/preload/array/.gulp.json
+++ b/test/fixtures/config/flags/preload/array/.gulp.js
@@ -1,6 +1,6 @@
-{
-  "preload": [
+module.exports = {
+  preload: [
     "./preload_one",
     "./preload_two"
   ]
-}
+};
diff --git a/test/fixtures/config/flags/preload/join-flags/.gulp.js b/test/fixtures/config/flags/preload/join-flags/.gulp.js
new file mode 100644
index 00000000..fe2a9b08
--- /dev/null
+++ b/test/fixtures/config/flags/preload/join-flags/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  preload: [
+    "./preload_two"
+  ]
+};
diff --git a/test/fixtures/config/flags/preload/join-flags/.gulp.json b/test/fixtures/config/flags/preload/join-flags/.gulp.json
deleted file mode 100644
index 63405ae5..00000000
--- a/test/fixtures/config/flags/preload/join-flags/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "preload": [
-    "./preload_two"
-  ]
-}
diff --git a/test/fixtures/config/flags/preload/string/.gulp.js b/test/fixtures/config/flags/preload/string/.gulp.js
new file mode 100644
index 00000000..cb913254
--- /dev/null
+++ b/test/fixtures/config/flags/preload/string/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  preload: "./preload"
+};
diff --git a/test/fixtures/config/flags/preload/string/.gulp.json b/test/fixtures/config/flags/preload/string/.gulp.json
deleted file mode 100644
index 22886303..00000000
--- a/test/fixtures/config/flags/preload/string/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "preload": "./preload"
-}
diff --git a/test/fixtures/config/flags/preload/with-cwd/.gulp.js b/test/fixtures/config/flags/preload/with-cwd/.gulp.js
new file mode 100644
index 00000000..e51966f4
--- /dev/null
+++ b/test/fixtures/config/flags/preload/with-cwd/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  preload: "../preload"
+};
diff --git a/test/fixtures/config/flags/preload/with-cwd/.gulp.json b/test/fixtures/config/flags/preload/with-cwd/.gulp.json
deleted file mode 100644
index c92f9743..00000000
--- a/test/fixtures/config/flags/preload/with-cwd/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "preload": "../preload"
-}
diff --git a/test/fixtures/config/flags/series/f/.gulp.js b/test/fixtures/config/flags/series/f/.gulp.js
new file mode 100644
index 00000000..6605aca5
--- /dev/null
+++ b/test/fixtures/config/flags/series/f/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    series: false
+  }
+};
diff --git a/test/fixtures/config/flags/series/f/.gulp.json b/test/fixtures/config/flags/series/f/.gulp.json
deleted file mode 100644
index 6da4dba0..00000000
--- a/test/fixtures/config/flags/series/f/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "series": false
-  }
-}
diff --git a/test/fixtures/config/flags/series/t/.gulp.js b/test/fixtures/config/flags/series/t/.gulp.js
new file mode 100644
index 00000000..f21fe066
--- /dev/null
+++ b/test/fixtures/config/flags/series/t/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    series: true
+  }
+};
diff --git a/test/fixtures/config/flags/series/t/.gulp.json b/test/fixtures/config/flags/series/t/.gulp.json
deleted file mode 100644
index 7f1f5a44..00000000
--- a/test/fixtures/config/flags/series/t/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "series": true
-  }
-}
diff --git a/test/fixtures/config/flags/silent/f/.gulp.js b/test/fixtures/config/flags/silent/f/.gulp.js
new file mode 100644
index 00000000..4630a77a
--- /dev/null
+++ b/test/fixtures/config/flags/silent/f/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    silent: false
+  }
+};
diff --git a/test/fixtures/config/flags/silent/f/.gulp.json b/test/fixtures/config/flags/silent/f/.gulp.json
deleted file mode 100644
index 4f3822ab..00000000
--- a/test/fixtures/config/flags/silent/f/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "silent": false
-  }
-}
diff --git a/test/fixtures/config/flags/silent/t/.gulp.js b/test/fixtures/config/flags/silent/t/.gulp.js
new file mode 100644
index 00000000..22486fd8
--- /dev/null
+++ b/test/fixtures/config/flags/silent/t/.gulp.js
@@ -0,0 +1,5 @@
+module.exports = {
+  flags: {
+    silent: true
+  }
+};
diff --git a/test/fixtures/config/flags/silent/t/.gulp.json b/test/fixtures/config/flags/silent/t/.gulp.json
deleted file mode 100644
index 9917bd8c..00000000
--- a/test/fixtures/config/flags/silent/t/.gulp.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "flags": {
-    "silent": true
-  }
-}
diff --git a/test/fixtures/config/flags/sortTasks/f/.gulp.js b/test/fixtures/config/flags/sortTasks/f/.gulp.js
new file mode 100644
index 00000000..e4640d82
--- /dev/null
+++ b/test/fixtures/config/flags/sortTasks/f/.gulp.js
@@ -0,0 +1,6 @@
+module.exports = {
+  gulpfile: "../../../../gulpfiles/gulpfile-4.js",
+  flags: {
+    sortTasks: false
+  }
+};
diff --git a/test/fixtures/config/flags/sortTasks/f/.gulp.json b/test/fixtures/config/flags/sortTasks/f/.gulp.json
deleted file mode 100644
index daa8a926..00000000
--- a/test/fixtures/config/flags/sortTasks/f/.gulp.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "gulpfile": "../../../../gulpfiles/gulpfile-4.js",
-  "flags": {
-    "sortTasks": false
-  }
-}
diff --git a/test/fixtures/config/flags/sortTasks/t/.gulp.js b/test/fixtures/config/flags/sortTasks/t/.gulp.js
new file mode 100644
index 00000000..aae6877b
--- /dev/null
+++ b/test/fixtures/config/flags/sortTasks/t/.gulp.js
@@ -0,0 +1,6 @@
+module.exports = {
+  gulpfile: "../../../../gulpfiles/gulpfile-4.js",
+  flags: {
+    sortTasks: true
+  }
+};
diff --git a/test/fixtures/config/flags/sortTasks/t/.gulp.json b/test/fixtures/config/flags/sortTasks/t/.gulp.json
deleted file mode 100644
index 254cd26a..00000000
--- a/test/fixtures/config/flags/sortTasks/t/.gulp.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "gulpfile": "../../../../gulpfiles/gulpfile-4.js",
-  "flags": {
-    "sortTasks": true
-  }
-}
diff --git a/test/fixtures/config/flags/tasksDepth/.gulp.js b/test/fixtures/config/flags/tasksDepth/.gulp.js
new file mode 100644
index 00000000..6960b163
--- /dev/null
+++ b/test/fixtures/config/flags/tasksDepth/.gulp.js
@@ -0,0 +1,6 @@
+module.exports = {
+  gulpfile: "../../../gulpfiles/gulpfile-4.js",
+  flags: {
+    tasksDepth: 4
+  }
+};
diff --git a/test/fixtures/config/flags/tasksDepth/.gulp.json b/test/fixtures/config/flags/tasksDepth/.gulp.json
deleted file mode 100644
index bc309203..00000000
--- a/test/fixtures/config/flags/tasksDepth/.gulp.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "gulpfile": "../../../gulpfiles/gulpfile-4.js",
-  "flags": {
-    "tasksDepth": 4
-  }
-}
diff --git a/test/fixtures/config/foo/bar/.gulp.js b/test/fixtures/config/foo/bar/.gulp.js
new file mode 100644
index 00000000..4c3e35e7
--- /dev/null
+++ b/test/fixtures/config/foo/bar/.gulp.js
@@ -0,0 +1,3 @@
+module.exports = {
+  description: "Description by .gulp.json in directory foo/bar"
+};
diff --git a/test/fixtures/config/foo/bar/.gulp.json b/test/fixtures/config/foo/bar/.gulp.json
deleted file mode 100644
index 186db419..00000000
--- a/test/fixtures/config/foo/bar/.gulp.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-  "description": "Description by .gulp.json in directory foo/bar"
-}
diff --git a/test/fixtures/gulpfiles/.gulp.js b/test/fixtures/gulpfiles/.gulp.js
index e82d59c2..a4eb937f 100644
--- a/test/fixtures/gulpfiles/.gulp.js
+++ b/test/fixtures/gulpfiles/.gulp.js
@@ -7,4 +7,4 @@ module.exports = {
       return "gulp-cli/test/fixtures/gulpfiles";
     }
   }
-}
+};