diff --git a/lib/validate.js b/lib/validate.js
index badb035ba..3370a9306 100644
--- a/lib/validate.js
+++ b/lib/validate.js
@@ -118,103 +118,112 @@ module.exports = {
       }
     }
 
-    // Default context
-    if (!this.webpackConfig.context) {
-      this.webpackConfig.context = this.serverless.config.servicePath;
-    }
-
-    // Default target
-    if (!this.webpackConfig.target) {
-      this.webpackConfig.target = 'node';
-    }
-
-    // Default output
-    if (!this.webpackConfig.output || _.isEmpty(this.webpackConfig.output)) {
-      const outputPath = path.join(this.serverless.config.servicePath, '.webpack');
-      this.webpackConfig.output = {
-        libraryTarget: 'commonjs',
-        path: outputPath,
-        filename: '[name].js',
-      };
-    }
+    const processConfig = _config => {
+      this.webpackConfig = _config;
+      // Default context
+      if (!this.webpackConfig.context) {
+        this.webpackConfig.context = this.serverless.config.servicePath;
+      }
 
-    // Custom output path
-    if (this.options.out) {
-      this.webpackConfig.output.path = path.join(this.serverless.config.servicePath, this.options.out);
-    }
+      // Default target
+      if (!this.webpackConfig.target) {
+        this.webpackConfig.target = 'node';
+      }
 
-    if (this.skipCompile) {
-      this.serverless.cli.log('Skipping build and using existing compiled output');
-      if (!fse.pathExistsSync(this.webpackConfig.output.path)) {
-        return BbPromise.reject(new this.serverless.classes
-          .Error('No compiled output found'));
+      // Default output
+      if (!this.webpackConfig.output || _.isEmpty(this.webpackConfig.output)) {
+        const outputPath = path.join(this.serverless.config.servicePath, '.webpack');
+        this.webpackConfig.output = {
+          libraryTarget: 'commonjs',
+          path: outputPath,
+          filename: '[name].js',
+        };
       }
-      this.keepOutputDirectory = true;
-    }
 
-    if (!this.keepOutputDirectory) {
-      this.options.verbose && this.serverless.cli.log(`Removing ${this.webpackConfig.output.path}`);
-      fse.removeSync(this.webpackConfig.output.path);
-    }
-    this.webpackOutputPath = this.webpackConfig.output.path;
+      // Custom output path
+      if (this.options.out) {
+        this.webpackConfig.output.path = path.join(this.serverless.config.servicePath, this.options.out);
+      }
 
-    // In case of individual packaging we have to create a separate config for each function
-    if (_.has(this.serverless, 'service.package') && this.serverless.service.package.individually) {
-      this.options.verbose && this.serverless.cli.log('Using multi-compile (individual packaging)');
-      this.multiCompile = true;
+      if (this.skipCompile) {
+        this.serverless.cli.log('Skipping build and using existing compiled output');
+        if (!fse.pathExistsSync(this.webpackConfig.output.path)) {
+          return BbPromise.reject(new this.serverless.classes
+            .Error('No compiled output found'));
+        }
+        this.keepOutputDirectory = true;
+      }
 
-      if (this.webpackConfig.entry && !_.isEqual(this.webpackConfig.entry, entries)) {
-        return BbPromise.reject(new this.serverless.classes
-          .Error('Webpack entry must be automatically resolved when package.individually is set to true. ' +
-            'In webpack.config.js, remove the entry declaration or set entry to slsw.lib.entries.'));
+      if (!this.keepOutputDirectory) {
+        this.options.verbose && this.serverless.cli.log(`Removing ${this.webpackConfig.output.path}`);
+        fse.removeSync(this.webpackConfig.output.path);
       }
+      this.webpackOutputPath = this.webpackConfig.output.path;
 
-      // Lookup associated Serverless functions
-      const allEntryFunctions = _.map(
-        this.serverless.service.getAllFunctions(),
-        funcName => {
-          const func = this.serverless.service.getFunction(funcName);
-          const handler = func.handler;
-          const handlerFile = path.relative('.', getHandlerFile(handler));
-          return {
-            handlerFile,
-            funcName,
-            func
-          };
+      // In case of individual packaging we have to create a separate config for each function
+      if (_.has(this.serverless, 'service.package') && this.serverless.service.package.individually) {
+        this.options.verbose && this.serverless.cli.log('Using multi-compile (individual packaging)');
+        this.multiCompile = true;
+
+        if (this.webpackConfig.entry && !_.isEqual(this.webpackConfig.entry, entries)) {
+          return BbPromise.reject(new this.serverless.classes
+            .Error('Webpack entry must be automatically resolved when package.individually is set to true. ' +
+              'In webpack.config.js, remove the entry declaration or set entry to slsw.lib.entries.'));
         }
-      );
 
-      this.entryFunctions = _.flatMap(entries, (value, key) => {
-        const entry = path.relative('.', value);
-        const entryFile = _.replace(entry, new RegExp(`${path.extname(entry)}$`), '');
+        // Lookup associated Serverless functions
+        const allEntryFunctions = _.map(
+          this.serverless.service.getAllFunctions(),
+          funcName => {
+            const func = this.serverless.service.getFunction(funcName);
+            const handler = func.handler;
+            const handlerFile = path.relative('.', getHandlerFile(handler));
+            return {
+              handlerFile,
+              funcName,
+              func
+            };
+          }
+        );
+
+        this.entryFunctions = _.flatMap(entries, (value, key) => {
+          const entry = path.relative('.', value);
+          const entryFile = _.replace(entry, new RegExp(`${path.extname(entry)}$`), '');
+
+          const entryFuncs = _.filter(allEntryFunctions, [ 'handlerFile', entryFile ]);
+          if (_.isEmpty(entryFuncs)) {
+            // We have to make sure that for each entry there is an entry function item.
+            entryFuncs.push({});
+          }
+          _.forEach(entryFuncs, entryFunc => {
+            entryFunc.entry = {
+              key,
+              value
+            };
+          });
+          return entryFuncs;
+        });
 
-        const entryFuncs = _.filter(allEntryFunctions, [ 'handlerFile', entryFile ]);
-        if (_.isEmpty(entryFuncs)) {
-          // We have to make sure that for each entry there is an entry function item.
-          entryFuncs.push({});
-        }
-        _.forEach(entryFuncs, entryFunc => {
-          entryFunc.entry = {
-            key,
-            value
+        this.webpackConfig = _.map(this.entryFunctions, entryFunc => {
+          const config = _.cloneDeep(this.webpackConfig);
+          config.entry = {
+            [entryFunc.entry.key]: entryFunc.entry.value
           };
+          const compileName = entryFunc.funcName || _.camelCase(entryFunc.entry.key);
+          config.output.path = path.join(config.output.path, compileName);
+          return config;
         });
-        return entryFuncs;
-      });
+      } else {
+        this.webpackConfig.output.path = path.join(this.webpackConfig.output.path, 'service');
+      }
 
-      this.webpackConfig = _.map(this.entryFunctions, entryFunc => {
-        const config = _.cloneDeep(this.webpackConfig);
-        config.entry = {
-          [entryFunc.entry.key]: entryFunc.entry.value
-        };
-        const compileName = entryFunc.funcName || _.camelCase(entryFunc.entry.key);
-        config.output.path = path.join(config.output.path, compileName);
-        return config;
-      });
-    } else {
-      this.webpackConfig.output.path = path.join(this.webpackConfig.output.path, 'service');
+      return BbPromise.resolve();
     }
 
-    return BbPromise.resolve();
+    if (this.webpackConfig instanceof Promise) {
+      this.webpackConfig.then(config => processConfig(config));
+    } else {
+      processConfig(this.webpackConfig);
+    }
   },
 };