diff --git a/common.mk b/common.mk
index 4c156b973a..0ff2a5486e 100644
--- a/common.mk
+++ b/common.mk
@@ -886,10 +886,8 @@ $(srcdir)/ext/json/parser/parser.c: $(srcdir)/ext/json/parser/parser.rl
 	$(Q) $(CHDIR) $(@D) && $(exec) $(MAKE) -f prereq.mk $(MFLAGS) \
 		Q=$(Q) ECHO=$(ECHO) top_srcdir=../../.. srcdir=. VPATH=../../.. BASERUBY="$(BASERUBY)"
 
-{$(VPATH)}ext/rbconfig/sizeof/sizes.c: $(srcdir)/ext/rbconfig/sizeof/depend \
+$(srcdir)/ext/rbconfig/sizeof/sizes.c: $(srcdir)/ext/rbconfig/sizeof/depend \
 		$(srcdir)/tool/generic_erb.rb $(srcdir)/template/sizes.c.tmpl $(srcdir)/configure.in
-
-ext/rbconfig/sizeof/sizes.c:
 	$(ECHO) generating $@
 	$(Q) $(CHDIR) $(@D) && \
 	sed '/AUTOGENERATED/q;s#{.*}##' depend | \