diff --git a/compiler-js/src/main/java/com/redhat/ceylon/compiler/js/loader/JsModuleSourceMapper.java b/compiler-js/src/main/java/com/redhat/ceylon/compiler/js/loader/JsModuleSourceMapper.java
index bd463336e35..483200ef9e4 100644
--- a/compiler-js/src/main/java/com/redhat/ceylon/compiler/js/loader/JsModuleSourceMapper.java
+++ b/compiler-js/src/main/java/com/redhat/ceylon/compiler/js/loader/JsModuleSourceMapper.java
@@ -168,7 +168,7 @@ public void resolveModule(final ArtifactResult artifact, final Module module,
             if ("npm".equals(artifact.namespace())) {
                 try {
                     final File root = ((AbstractRepository)artifact.repository()).getRoot().getContent(File.class);
-                    final String npmPath = artifact.artifact().getAbsolutePath();
+                    final String npmPath = artifact.artifact().getAbsolutePath().replaceAll(File.separator, "/");
                     ((JsonModule)module).setNpmPath(npmPath.substring(root.getAbsolutePath().length()+1));
                     module.setJsMajor(Versions.JS_BINARY_MAJOR_VERSION);
                     module.setJsMinor(Versions.JS_BINARY_MINOR_VERSION);