diff --git a/src/helpers.js b/src/helpers.js
index 5db1765..3013587 100644
--- a/src/helpers.js
+++ b/src/helpers.js
@@ -43,6 +43,27 @@ function normalize (path) {
 	return resolvedParts.join('/');
 }
 
+function join () {
+    if (arguments.length === 0)
+      return '.';
+
+    let joined;
+    for (let i = 0; i < arguments.length; ++i) {
+      let arg = arguments[i];
+      if (arg.length > 0) {
+        if (joined === undefined)
+          joined = arg;
+        else
+          joined += '/' + arg;
+      }
+    }
+
+    if (joined === undefined)
+      return '.';
+  
+    return joined;
+}
+
 export function commonjsRequire (path, originalModuleDir) {
 	const isRelative = path[0] === '.' || path[0] === '/';
 	path = normalize(path);
@@ -53,8 +74,7 @@ export function commonjsRequire (path, originalModuleDir) {
 		} else if (originalModuleDir) {
 			relPath = normalize(originalModuleDir + '/node_modules/' + path);
 		} else {
-		  throw new Error('Missing test case');
-			// relPath = pathModule.normalize(pathModule.join('node_modules', path));
+			relPath = normalize(join('node_modules', path));
 		}
 		for (let extensionIndex = 0; extensionIndex < CHECKED_EXTENSIONS.length; extensionIndex++) {
 			const resolvedPath = relPath + CHECKED_EXTENSIONS[extensionIndex];
diff --git a/test/function/dynamic-require-package-sub/_config.js b/test/function/dynamic-require-package-sub/_config.js
new file mode 100644
index 0000000..790feee
--- /dev/null
+++ b/test/function/dynamic-require-package-sub/_config.js
@@ -0,0 +1,14 @@
+const nodeResolve = require('rollup-plugin-node-resolve');
+
+module.exports = {
+	input: 'sub/entry.js',
+	description: 'resolves imports of node_modules from subdirectories',
+	options: {
+		plugins: [nodeResolve()]
+	},
+	pluginOptions: {
+		dynamicRequireTargets: [
+			'function/dynamic-require-package-sub/node_modules/custom-module/**'
+		]
+	}
+};
diff --git a/test/function/dynamic-require-package-sub/node_modules/custom-module/entry.js b/test/function/dynamic-require-package-sub/node_modules/custom-module/entry.js
new file mode 100644
index 0000000..f67b073
--- /dev/null
+++ b/test/function/dynamic-require-package-sub/node_modules/custom-module/entry.js
@@ -0,0 +1 @@
+module.exports = 'custom-module';
diff --git a/test/function/dynamic-require-package-sub/node_modules/custom-module/package.json b/test/function/dynamic-require-package-sub/node_modules/custom-module/package.json
new file mode 100644
index 0000000..382adf7
--- /dev/null
+++ b/test/function/dynamic-require-package-sub/node_modules/custom-module/package.json
@@ -0,0 +1 @@
+{"main": "./entry.js"}
diff --git a/test/function/dynamic-require-package-sub/package.json b/test/function/dynamic-require-package-sub/package.json
new file mode 100644
index 0000000..e5efa20
--- /dev/null
+++ b/test/function/dynamic-require-package-sub/package.json
@@ -0,0 +1 @@
+{"main": "./sub/entry.js"}
diff --git a/test/function/dynamic-require-package-sub/sub/entry.js b/test/function/dynamic-require-package-sub/sub/entry.js
new file mode 100644
index 0000000..e071586
--- /dev/null
+++ b/test/function/dynamic-require-package-sub/sub/entry.js
@@ -0,0 +1,2 @@
+
+assert.equal(require('custom-module'), 'custom-module');
diff --git a/test/test.js b/test/test.js
index 6a50707..a724677 100644
--- a/test/test.js
+++ b/test/test.js
@@ -120,7 +120,7 @@ describe('rollup-plugin-commonjs', () => {
 			(config.solo ? it.only : it)(dir, async () => {
 				const options = Object.assign(
 					{
-						input: `function/${dir}/main.js`
+						input: `function/${dir}/${config.input || 'main.js'}`
 					},
 					config.options || {},
 					{