diff --git a/ext/syck/depend b/ext/syck/depend
index f05bef303f..3eec4de72a 100644
--- a/ext/syck/depend
+++ b/ext/syck/depend
@@ -2,7 +2,7 @@ ruby_headers = $(hdrdir)/ruby.h $(topdir)/config.h $(hdrdir)/defines.h \
   $(hdrdir)/missing.h $(hdrdir)/intern.h $(hdrdir)/st.h
 bytecode.o: bytecode.c syck.h gram.h $(ruby_headers)
 emitter.o: emitter.c syck.h $(ruby_headers)
-gram.o: gram.c syck.h st.h
+gram.o: gram.c syck.h $(hdrdir)/st.h
 handler.o: handler.c syck.h $(ruby_headers)
 implicit.o: implicit.c syck.h $(ruby_headers)
 node.o: node.c syck.h $(ruby_headers)