Actually moving this to the proper place.
diff --git a/package.json b/package.json
index f02a100..51b3e12 100644
--- a/package.json
+++ b/package.json
@@ -373,6 +373,7 @@
     "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",
     "third_party/zlib/crc32.h",