diff --git a/ext/fiddle/function.c b/ext/fiddle/function.c
index e0da8b6..e843587 100644
--- a/ext/fiddle/function.c
+++ b/ext/fiddle/function.c
@@ -186,7 +186,7 @@ function_call(int argc, VALUE argv[], VALUE self)
 
     rb_funcall(mFiddle, rb_intern("last_error="), 1, INT2NUM(errno));
 #if defined(_WIN32)
-    rb_funcall(mFiddle, rb_intern("win32_last_error="), 1, INT2NUM(errno));
+    rb_funcall(mFiddle, rb_intern("win32_last_error="), 1, ULONG2NUM(GetLastError()));
 #endif
 
     ALLOCV_END(alloc_buffer);
diff --git a/test/fiddle/test_function.rb b/test/fiddle/test_function.rb
index de7c958..0e96fe4 100644
--- a/test/fiddle/test_function.rb
+++ b/test/fiddle/test_function.rb
@@ -10,6 +10,7 @@ module Fiddle
     def setup
       super
       Fiddle.last_error = nil
+      Fiddle.win32_last_error = nil if WINDOWS
     end
 
     def test_default_abi
@@ -65,6 +66,18 @@ module Fiddle
       refute_nil Fiddle.last_error
     end
 
+    def test_win32_last_error
+      kernel32 = dlopen('kernel32')
+      args = [kernel32['SetLastError'], [TYPE_LONG], TYPE_VOID]
+      args << Function::STDCALL if Function.const_defined?(:STDCALL)
+      func = Function.new(*args)
+
+      assert_nil(Fiddle.win32_last_error)
+      n = 1 << 29 | 1
+      func.call(n)
+      assert_equal(n, Fiddle.win32_last_error)
+    end if WINDOWS
+
     def test_strcpy
       f = Function.new(@libc['strcpy'], [TYPE_VOIDP, TYPE_VOIDP], TYPE_VOIDP)
       buff = "000"