Actually moving this to the proper place.
diff --git a/binding.gyp b/binding.gyp
index 651c2e1..4234f62 100644
--- a/binding.gyp
+++ b/binding.gyp
@@ -699,6 +699,7 @@
         'src/core/census/context.c',
         'src/core/census/initialize.c',
         'src/core/census/operation.c',
+        'src/core/census/placeholders.c',
         'src/core/census/tag_set.c',
         'src/core/census/tracing.c',
       ],