diff --git a/lib/executor.js b/lib/executor.js
index 428d3de..a3f13ec 100644
--- a/lib/executor.js
+++ b/lib/executor.js
@@ -322,7 +322,6 @@ function setupMiddleware(app, instructions) {
 }
 
 function getUpdatedConfigObject(app, config) {
-
   var DYNAMIC_CONFIG_PARAM = /\$\{(\w+)\}$/;
 
   function getConfigVariable(param) {
@@ -341,11 +340,24 @@ function getUpdatedConfigObject(app, config) {
   }
 
   function interpolateVariables(config) {
+    // config is a string and contains a config variable ('${var}')
+    if (typeof config === 'string')
+      return getConfigVariable(config);
+
+    // anything but an array or object
+    if (typeof config !== 'object' || config == null)
+      return config;
+
+    // recurse into array elements
+    if (Array.isArray(config))
+      return config.map(interpolateVariables);
+
+    // recurse into object props
     var interpolated = {};
     Object.keys(config).forEach(function(configKey) {
       var value = config[configKey];
       if (Array.isArray(value)) {
-        interpolated[configKey] = value.map(getConfigVariable);
+        interpolated[configKey] = value.map(interpolateVariables);
       } else if (typeof value === 'string') {
         interpolated[configKey] = getConfigVariable(value);
       } else if (typeof value === 'object' && Object.keys(value).length) {
diff --git a/test/executor.test.js b/test/executor.test.js
index 5ecb977..f826a1f 100644
--- a/test/executor.test.js
+++ b/test/executor.test.js
@@ -1,3 +1,4 @@
+var async = require('async');
 var boot = require('../');
 var path = require('path');
 var loopback = require('loopback');
@@ -426,7 +427,6 @@ describe('executor', function() {
   });
 
   describe('with middleware.json', function() {
-
     it('should parse a simple config variable', function(done) {
       boot.execute(app, simpleMiddlewareConfig('routes',
         { path: '${restApiRoot}' }
@@ -494,6 +494,37 @@ describe('executor', function() {
       });
     });
 
+    it('should not parse invalid config variables', function(done) {
+      var invalidDataTypes = [undefined, function() {}];
+      async.each(invalidDataTypes, function(invalidDataType, cb) {
+        var config = simpleMiddlewareConfig('routes', {
+          path: invalidDataType
+        });
+        boot.execute(app, config);
+
+        supertest(app)
+          .get('/')
+          .end(function(err, res) {
+            expect(err).to.be.null();
+            expect(res.body.path).to.be.undefined();
+            cb();
+          });
+      }, done);
+    });
+
+    it('should parse valid config variables', function(done) {
+      var config = simpleMiddlewareConfig('routes', {
+        props: ['a', '${vVar}', 1, true, function() {}, {x:1, y: '${y}'}]
+      });
+      boot.execute(app, config);
+
+      supertest(app)
+        .get('/')
+        .end(function(err, res) {
+          expect(err).to.be.null();
+          done();
+        });
+    });
   });
 
   describe('with component-config.json', function() {