diff --git a/src/org/mozilla/javascript/commonjs/module/provider/UrlModuleSourceProvider.java b/src/org/mozilla/javascript/commonjs/module/provider/UrlModuleSourceProvider.java
index b1b6ff2f17..fba9bc3b9b 100644
--- a/src/org/mozilla/javascript/commonjs/module/provider/UrlModuleSourceProvider.java
+++ b/src/org/mozilla/javascript/commonjs/module/provider/UrlModuleSourceProvider.java
@@ -130,7 +130,7 @@ protected ModuleSource loadFromUri(URI uri, URI base, Object validator)
     protected ModuleSource loadFromActualUri(URI uri, URI base, Object validator)
     throws IOException
     {
-        final URL url = new URL(base.toURL(), uri.toString());
+        final URL url = new URL(base == null ? null : base.toURL(), uri.toString());
         final long request_time = System.currentTimeMillis();
         final URLConnection urlConnection = openUrlConnection(url);
         final URLValidator applicableValidator;