Fixed

src/lib/Manifest.vala

@@ -94,7 +94,7 @@ namespace Usm {
                     provides[new ResourceRef(pair.key)] = new ManifestFile.from_string(pair.value.as<string>());
                 }
                 else {
-                    provides[new ResourceRef(pair.key)] = mapper.materialise(obj);
+                    provides[new ResourceRef(pair.key)] = mapper.materialise(pair.value.as<Properties>());
                 }
             }
         }