diff --git a/tool/expand-config.rb b/tool/expand-config.rb
new file mode 100755
index 0000000000..fb2edd02e8
--- /dev/null
+++ b/tool/expand-config.rb
@@ -0,0 +1,7 @@
+STDOUT.binmode
+ARGF.each do |line|
+  line.gsub!(/@([a-z_]\w*)@/i) {
+    (RbConfig::MAKEFILE_CONFIG[$1] or "").gsub(/\$\((.+?)\)/, %Q[${\\1}])
+  }
+  puts line
+end
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index a04e8024be..010bf4b630 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -1053,11 +1053,7 @@ end
 <<KEEP
 
 $(ruby_pc): $(RBCONFIG)
-	@$(MINIRUBY) -r./rbconfig -p \
-	-e 'STDOUT.binmode' \
-	-e '$$_.gsub!(/@([a-z_]\w*)@/i) {' \
-	-e '(RbConfig::MAKEFILE_CONFIG[$$1] or "").gsub(/\$$\((.+?)\)/, %Q[$${\\1}])' \
-	-e '}' \
+	@$(MINIRUBY) -r./rbconfig $(srcdir)/tool/expand-config.rb \
 	$(srcdir)/template/ruby.pc.in > $@
 
 {$(srcdir)/enc}.c.obj: