Actually moving this to the proper place.
diff --git a/BUILD b/BUILD
index 459aebd..23a4a94 100644
--- a/BUILD
+++ b/BUILD
@@ -438,6 +438,7 @@
     "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",
   ],
@@ -714,6 +715,7 @@
     "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",
   ],
@@ -1388,6 +1390,7 @@
     "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",
   ],