diff --git a/ext/json/generator/depend b/ext/json/generator/depend
index 1a042a2501..1f0ea0a624 100644
--- a/ext/json/generator/depend
+++ b/ext/json/generator/depend
@@ -1 +1 @@
-generator.o: generator.c generator.h $(srcdir)/../fbuffer/fbuffer.h
+generator.o: generator.c generator.h $(srcdir)/../fbuffer/fbuffer.h $(ruby_headers)