diff --git a/ext/fiddle/closure.c b/ext/fiddle/closure.c
index 1a80b2b02a..2044c836ea 100644
--- a/ext/fiddle/closure.c
+++ b/ext/fiddle/closure.c
@@ -14,10 +14,7 @@ typedef struct {
 } fiddle_closure;
 
 #if defined(USE_FFI_CLOSURE_ALLOC)
-#elif defined(__OpenBSD__) || defined(__APPLE__) || defined(__linux__)
-# define USE_FFI_CLOSURE_ALLOC 0
-#elif defined(RUBY_LIBFFI_MODVERSION) && RUBY_LIBFFI_MODVERSION < 3000005 && \
-	(defined(__i386__) || defined(__x86_64__) || defined(_M_IX86) || defined(_M_AMD64))
+#elif !defined(HAVE_FFI_CLOSURE_ALLOC)
 # define USE_FFI_CLOSURE_ALLOC 0
 #else
 # define USE_FFI_CLOSURE_ALLOC 1
diff --git a/ext/fiddle/extconf.rb b/ext/fiddle/extconf.rb
index fce0cb4079..915afb986e 100644
--- a/ext/fiddle/extconf.rb
+++ b/ext/fiddle/extconf.rb
@@ -13,7 +13,7 @@ if ! bundle
   if have_header(ffi_header = 'ffi.h')
     true
   elsif have_header(ffi_header = 'ffi/ffi.h')
-    $defs.push(format('-DUSE_HEADER_HACKS'))
+    $defs.push('-DUSE_HEADER_HACKS')
     true
   end and (have_library('ffi') || have_library('libffi'))
 end or
@@ -135,6 +135,7 @@ elsif have_header "windows.h"
 end
 
 have_const('FFI_STDCALL', ffi_header)
+have_func('ffi_closure_alloc', ffi_header)
 
 config = File.read(RbConfig.expand(File.join($arch_hdrdir, "ruby/config.h")))
 types = {"SIZE_T"=>"SSIZE_T", "PTRDIFF_T"=>nil, "INTPTR_T"=>nil}
@@ -142,7 +143,7 @@ types.each do |type, signed|
   if /^\#define\s+SIZEOF_#{type}\s+(SIZEOF_(.+)|\d+)/ =~ config
     if size = $2 and size != 'VOIDP'
       size = types.fetch(size) {size}
-      $defs << format("-DTYPE_%s=TYPE_%s", signed||type, size)
+      $defs << "-DTYPE_#{signed||type}=TYPE_#{size}"
     end
     if signed
       check_signedness(type.downcase, "stddef.h")