diff --git a/common.mk b/common.mk
index f8ab233d69..e94c4756ea 100644
--- a/common.mk
+++ b/common.mk
@@ -102,7 +102,6 @@ COMMONOBJS    = array.$(OBJEXT) \
 EXPORTOBJS    = $(DLNOBJ) \
 		localeinit.$(OBJEXT) \
 		loadpath.$(OBJEXT) \
-		sizes.$(OBJEXT) \
 		$(COMMONOBJS)
 
 OBJS          = $(EXPORTOBJS) prelude.$(OBJEXT)
@@ -881,10 +880,10 @@ INSNS2VMOPT = --srcdir="$(srcdir)"
 
 {$(VPATH)}vm.inc: $(srcdir)/template/vm.inc.tmpl
 
-srcs: {$(VPATH)}parse.c {$(VPATH)}lex.c {$(VPATH)}newline.c {$(VPATH)}id.c {$(VPATH)}sizes.c srcs-ext srcs-enc
+srcs: {$(VPATH)}parse.c {$(VPATH)}lex.c {$(VPATH)}newline.c {$(VPATH)}id.c srcs-ext srcs-enc
 
 EXT_SRCS = $(srcdir)/ext/ripper/ripper.c $(srcdir)/ext/json/parser/parser.c \
-	   $(srcdir)/ext/dl/callback/callback.c
+	   $(srcdir)/ext/dl/callback/callback.c  $(srcdir)/ext/rbconfig/sizeof/sizes.c
 
 srcs-ext: $(EXT_SRCS)
 
@@ -908,11 +907,6 @@ id.c: $(srcdir)/tool/generic_erb.rb $(srcdir)/template/id.c.tmpl $(srcdir)/defs/
 	$(Q) $(BASERUBY) $(srcdir)/tool/generic_erb.rb --output=$@ \
 		$(srcdir)/template/id.c.tmpl
 
-sizes.c: $(srcdir)/tool/generic_erb.rb $(srcdir)/template/sizes.c.tmpl $(srcdir)/configure.in
-	$(ECHO) generating $@
-	$(Q) $(BASERUBY) $(srcdir)/tool/generic_erb.rb --output=$@ \
-		$(srcdir)/template/sizes.c.tmpl $(srcdir)/configure.in
-
 node_name.inc: {$(VPATH)}node.h
 	$(ECHO) generating $@
 	$(Q) $(BASERUBY) -n $(srcdir)/tool/node_name.rb < $? > $@
@@ -978,6 +972,12 @@ $(srcdir)/ext/dl/callback/callback.c: $(srcdir)/ext/dl/callback/mkcallback.rb $(
 	$(Q) $(CHDIR) $(@D) && $(exec) $(MAKE) -f depend $(MFLAGS) \
 		Q=$(Q) ECHO=$(ECHO) top_srcdir=../.. srcdir=. VPATH=../.. RUBY="$(BASERUBY)"
 
+$(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) && $(exec) $(MAKE) -f depend $(MFLAGS) \
+		Q=$(Q) ECHO=$(ECHO) top_srcdir=../../.. srcdir=. VPATH=../../.. RUBY="$(BASERUBY)"
+
 ##
 
 run: fake miniruby$(EXEEXT) PHONY
diff --git a/ext/rbconfig/sizeof/depend b/ext/rbconfig/sizeof/depend
new file mode 100644
index 0000000000..360b3386d3
--- /dev/null
+++ b/ext/rbconfig/sizeof/depend
@@ -0,0 +1,3 @@
+sizes.c: $(top_srcdir)/tool/generic_erb.rb $(top_srcdir)/template/sizes.c.tmpl $(top_srcdir)/configure.in
+	$(Q) $(RUBY) $(top_srcdir)/tool/generic_erb.rb --output=$@ \
+		$(top_srcdir)/template/sizes.c.tmpl $(top_srcdir)/configure.in
diff --git a/ext/rbconfig/sizeof/extconf.rb b/ext/rbconfig/sizeof/extconf.rb
new file mode 100644
index 0000000000..619b4256f8
--- /dev/null
+++ b/ext/rbconfig/sizeof/extconf.rb
@@ -0,0 +1,2 @@
+$srcs = %w[sizes.c]
+create_makefile('rbconfig/sizeof')
diff --git a/inits.c b/inits.c
index f6611a010d..fe0aade090 100644
--- a/inits.c
+++ b/inits.c
@@ -61,6 +61,5 @@ rb_call_inits(void)
     CALL(Complex);
     CALL(version);
     CALL(vm_trace);
-    CALL(sizes);
 }
 #undef CALL
diff --git a/miniinit.c b/miniinit.c
index 6d285aea64..bc6138a774 100644
--- a/miniinit.c
+++ b/miniinit.c
@@ -28,9 +28,3 @@ Init_enc_set_filesystem_encoding(void)
 {
     return rb_enc_to_index(rb_default_external_encoding());
 }
-
-/* sizes.c */
-void
-Init_sizes(void)
-{
-}
diff --git a/template/sizes.c.tmpl b/template/sizes.c.tmpl
index e47eadebb7..ac9964dd5b 100644
--- a/template/sizes.c.tmpl
+++ b/template/sizes.c.tmpl
@@ -12,7 +12,7 @@ conditions = {
 }
 %>
 void
-Init_sizes(void)
+Init_sizeof(void)
 {
     VALUE s = rb_hash_new();
     rb_define_const(rb_define_module("RbConfig"), "SIZEOF", s);
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index cd41a3a5df..216fb9dcf3 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -1127,8 +1127,6 @@ probes.h: {$(VPATH)}probes.dmyh
 	  $(Q) $(CP) $(srcdir:/=\)\probes.dmyh $(OS_DEST_FILE)\
 	)
 
-{$(VPATH)}sizes.c: sizes.c
-
 INSNS	= opt_sc.inc optinsn.inc optunifs.inc insns.inc insns_info.inc \
 	  vmtc.inc vm.inc