diff --git a/Tuprules.tup b/Tuprules.tup
index ecbf986..92f76c2 100644
--- a/Tuprules.tup
+++ b/Tuprules.tup
@@ -20,3 +20,6 @@ NIM_FLAGS = --noNimblePath
 
 !preserves_schema_nim = | $(BIN_DIR)/<preserves_schema_nim> |> ^o generate nim module %B^ $(BIN_DIR)/preserves_schema_nim %f |> %B.nim
 !preserves_schemac = | $(BIN_DIR)/<schemac> |> ^o^ $(BIN_DIR)/schemac |>
+
+SYNDICATE_CONFIG_DIR = $(TUP_CWD)/config
+!assert_built = |> ^ <built "%b" …>^ echo "<built \"%b\" \"`b2sum -l 32 $f | { read sum rest ; echo $sum; }`\">" > %o |> $(SYNDICATE_CONFIG_DIR)/built/%b.pr