--- a/src/runtime/Config.alpha-osf1
+++ b/src/runtime/Config.alpha-osf1
@@ -39,3 +39,7 @@
 OS_LIBS = #-ldl
 
 GC_SRC = cheneygc.c
+
+# Nothing to do for after-grovel-headers.
+.PHONY: after-grovel-headers
+after-grovel-headers: