diff --git a/README.md b/README.md
index bd6c7def..9b6515ad 100644
--- a/README.md
+++ b/README.md
@@ -278,6 +278,12 @@ interface Context {
   sourceMap: any
   /** Resource path */
   id: string
+  /** Files to watch */
+  dependencies: Set<string>
+  /** Emit a waring */
+  warn: PluginContext.warn
+  /** https://rollupjs.org/guide/en#plugin-context */
+  plugin: PluginContext
 }
 
 interface Payload {
diff --git a/src/index.js b/src/index.js
index af1102f3..3d46eae7 100644
--- a/src/index.js
+++ b/src/index.js
@@ -66,12 +66,24 @@ export default (options = {}) => {
         options.onImport(id)
       }
 
-      const res = await loaders.process({
-        code,
-        map: undefined,
+      const loaderContext = {
         id,
-        sourceMap
-      })
+        sourceMap,
+        dependencies: new Set(),
+        warn: this.warn.bind(this),
+        plugin: this
+      }
+      const res = await loaders.process(
+        {
+          code,
+          map: undefined
+        },
+        loaderContext
+      )
+
+      for (const dep of loaderContext.dependencies) {
+        this.addWatchFile(dep)
+      }
 
       if (postcssLoaderOptions.extract) {
         extracted.set(id, res.extracted)
diff --git a/src/less-loader.js b/src/less-loader.js
index 98b9d38b..e9b721b6 100644
--- a/src/less-loader.js
+++ b/src/less-loader.js
@@ -8,12 +8,16 @@ export default {
   async process({ code }) {
     const less = importCwd('less')
 
-    let { css, map } = await pify(less.render.bind(less))(code, {
+    let { css, map, imports } = await pify(less.render.bind(less))(code, {
       ...this.options,
       sourceMap: this.sourceMap && {},
       filename: this.id
     })
 
+    for (const dep of imports) {
+      this.dependencies.add(dep)
+    }
+
     if (map) {
       map = JSON.parse(map)
       map.sources = map.sources.map(source => humanlizePath(source))
diff --git a/src/loaders.js b/src/loaders.js
index 309933e3..ee9e0c22 100644
--- a/src/loaders.js
+++ b/src/loaders.js
@@ -57,22 +57,44 @@ export default class Loaders {
     })
   }
 
-  process({ code, map, id, sourceMap }) {
-    return series(this.use.slice().reverse().map(([name, options]) => {
-      const loader = this.getLoader(name)
-      const loaderContext = {
-        options: options || {},
-        id,
-        sourceMap
-      }
-      return v => {
-        if (loader.alwaysProcess || matchFile(id, loader.test)) {
-          return loader.process.call(loaderContext, v)
-        }
-        // Otherwise directly return input value
-        return v
-      }
-    }), { code, map })
+  /**
+   * Process the resource with loaders in serial
+   * @param {object} resource
+   * @param {string} resource.code
+   * @param {any} resource.map
+   * @param {object} context
+   * @param {string} context.id The absolute path to resource
+   * @param {boolean | 'inline'} context.sourceMap
+   * @param {Set<string>} context.dependencies A set of dependencies to watch
+   * @returns {{code: string, map?: any}}
+   */
+  process({ code, map }, context) {
+    return series(
+      this.use
+        .slice()
+        .reverse()
+        .map(([name, options]) => {
+          const loader = this.getLoader(name)
+          const loaderContext = Object.assign(
+            {
+              options: options || {}
+            },
+            context
+          )
+
+          return v => {
+            if (
+              loader.alwaysProcess ||
+              matchFile(loaderContext.id, loader.test)
+            ) {
+              return loader.process.call(loaderContext, v)
+            }
+            // Otherwise directly return input value
+            return v
+          }
+        }),
+      { code, map }
+    )
   }
 
   getLoader(name) {
diff --git a/src/postcss-loader.js b/src/postcss-loader.js
index bae6ad24..9d95c4b3 100644
--- a/src/postcss-loader.js
+++ b/src/postcss-loader.js
@@ -85,7 +85,10 @@ export default {
           ...options.modules,
           getJSON(filepath, json, outpath) {
             modulesExported[filepath] = json
-            if (typeof options.modules === 'object' && typeof options.modules.getJSON === 'function') {
+            if (
+              typeof options.modules === 'object' &&
+              typeof options.modules.getJSON === 'function'
+            ) {
               return options.modules.getJSON(filepath, json, outpath)
             }
           }
@@ -121,6 +124,17 @@ export default {
     }
 
     const res = await postcss(plugins).process(code, postcssOpts)
+
+    for (const msg of res.messages) {
+      if (msg.type === 'dependency') {
+        this.dependencies.add(msg.file)
+      }
+    }
+
+    for (const warning of res.warnings()) {
+      this.warn(warning)
+    }
+
     const outputMap = res.map && JSON.parse(res.map.toString())
     if (outputMap && outputMap.sources) {
       outputMap.sources = outputMap.sources.map(v => normalizePath(v))
@@ -142,7 +156,7 @@ export default {
         // But skip this when namedExports is a function
         // Since a user like you can manually log that if you want
         if (name !== newName && typeof options.namedExports !== 'function') {
-          console.warn(
+          this.warn(
             `Exported "${name}" as "${newName}" in ${humanlizePath(this.id)}`
           )
         }
diff --git a/src/sass-loader.js b/src/sass-loader.js
index d0d6cdef..9cc077c4 100644
--- a/src/sass-loader.js
+++ b/src/sass-loader.js
@@ -59,7 +59,10 @@ export default {
               resolvePromise(partialUrl, options)
                 .then(finishImport)
                 .catch(err => {
-                  if (err.code === 'MODULE_NOT_FOUND' || err.code === 'ENOENT') {
+                  if (
+                    err.code === 'MODULE_NOT_FOUND' ||
+                    err.code === 'ENOENT'
+                  ) {
                     resolvePromise(moduleUrl, options)
                       .then(finishImport)
                       .catch(next)
@@ -69,12 +72,17 @@ export default {
                 })
             }
           ].concat(this.options.importer || [])
-        }).then(res =>
-          resolve({
-            code: res.css.toString(),
-            map: res.map && res.map.toString()
+        })
+          .then(res => {
+            for (const file of res.stats.includedFiles) {
+              this.dependencies.add(file)
+            }
+            resolve({
+              code: res.css.toString(),
+              map: res.map && res.map.toString()
+            })
           })
-        ).catch(reject)
+          .catch(reject)
       )
     })
   }
diff --git a/src/stylus-loader.js b/src/stylus-loader.js
index 439ca2fa..001a5979 100644
--- a/src/stylus-loader.js
+++ b/src/stylus-loader.js
@@ -14,6 +14,10 @@ export default {
     })
 
     const css = await pify(style.render.bind(style))()
+    const deps = style.deps()
+    for (const dep of deps) {
+      this.dependencies.add(dep)
+    }
 
     return {
       code: css,