--- a/src/runtime/Config.x86-sunos
+++ b/src/runtime/Config.x86-sunos
@@ -13,3 +13,6 @@
 
 GC_SRC= gencgc.c
 
+# Nothing to do for after-grovel-headers.
+.PHONY: after-grovel-headers
+after-grovel-headers: