--- a/src/runtime/Config.x86_64-linux
+++ b/src/runtime/Config.x86_64-linux
@@ -37,3 +37,7 @@
 CFLAGS += -fno-omit-frame-pointer
 
 GC_SRC = gencgc.c
+
+# Nothing to do for after-grovel-headers.
+.PHONY: after-grovel-headers
+after-grovel-headers: