diff --git a/common.mk b/common.mk
index 4ede19cff6..e4d7bdae95 100644
--- a/common.mk
+++ b/common.mk
@@ -887,7 +887,7 @@ $(srcdir)/ext/rbconfig/sizeof/sizes.c: $(srcdir)/ext/rbconfig/sizeof/depend \
 		$(srcdir)/tool/generic_erb.rb $(srcdir)/template/sizes.c.tmpl $(srcdir)/configure.in
 	$(ECHO) generating $@
 	$(Q) $(CHDIR) $(@D) && \
-	sed /AUTOGENERATED/q depend | \
+	sed '/AUTOGENERATED/q;s#{.*}##' depend | \
 	$(exec) $(MAKE) -f - $(MFLAGS) \
 		Q=$(Q) ECHO=$(ECHO) top_srcdir=../../.. srcdir=. VPATH=../../.. RUBY="$(BASERUBY)"
 
diff --git a/ext/rbconfig/sizeof/depend b/ext/rbconfig/sizeof/depend
index 56564b1b99..4243785d43 100644
--- a/ext/rbconfig/sizeof/depend
+++ b/ext/rbconfig/sizeof/depend
@@ -1,4 +1,7 @@
-sizes.c: $(top_srcdir)/tool/generic_erb.rb $(top_srcdir)/template/sizes.c.tmpl $(top_srcdir)/configure.in $(top_srcdir)/ext/rbconfig/sizeof/extconf.rb
+{$(VPATH)}sizes.c: $(top_srcdir)/tool/generic_erb.rb \
+		   $(top_srcdir)/template/sizes.c.tmpl \
+		   $(top_srcdir)/configure.in \
+		   $(top_srcdir)/ext/rbconfig/sizeof/extconf.rb
 	$(Q) $(RUBY) $(top_srcdir)/tool/generic_erb.rb --output=$@ \
 		$(top_srcdir)/template/sizes.c.tmpl \
                 $(top_srcdir)/configure.in \