diff --git a/src/Module.js b/src/Module.js
index 96d6869..3a5350e 100644
--- a/src/Module.js
+++ b/src/Module.js
@@ -76,6 +76,14 @@ class SyntheticNamespaceDeclaration {
 
 			const original = this.originals[ reference.name ];
 
+			// throw with an informative error message if the reference doesn't exist.
+			if ( !original ) {
+				const err = new Error( `Export '${reference.name}' is not defined by '${this.module.id}'` );
+				err.code = 'MISSING_EXPORT';
+				err.file = this.module.id;
+				throw err;
+			}
+
 			original.addReference( reference );
 			return;
 		}
diff --git a/test/function/namespace-missing-export/_config.js b/test/function/namespace-missing-export/_config.js
new file mode 100644
index 0000000..963724b
--- /dev/null
+++ b/test/function/namespace-missing-export/_config.js
@@ -0,0 +1,9 @@
+var assert = require( 'assert' );
+var path = require( 'path' );
+
+module.exports = {
+	error: function ( err ) {
+		assert.equal( path.normalize( err.file ), path.resolve( __dirname, 'empty.js' ) );
+		assert.ok( /Export 'foo' is not defined by/.test( err.message ) );
+	}
+};
diff --git a/test/function/namespace-missing-export/empty.js b/test/function/namespace-missing-export/empty.js
new file mode 100644
index 0000000..e69de29
diff --git a/test/function/namespace-missing-export/main.js b/test/function/namespace-missing-export/main.js
new file mode 100644
index 0000000..bfb885d
--- /dev/null
+++ b/test/function/namespace-missing-export/main.js
@@ -0,0 +1,3 @@
+import * as mod from './empty.js';
+
+mod.foo();