diff --git a/internal.h b/internal.h
index 85370ec0d7..6cab3d4ffd 100644
--- a/internal.h
+++ b/internal.h
@@ -1348,6 +1348,8 @@ VALUE rb_io_flush_raw(VALUE, int);
 size_t rb_io_memsize(const rb_io_t *);
 #endif
 int rb_stderr_tty_p(void);
+void rb_io_fptr_finalize_internal(void *ptr);
+#define rb_io_fptr_finalize rb_io_fptr_finalize_internal
 
 /* load.c */
 VALUE rb_get_load_path(void);
diff --git a/io.c b/io.c
index 56332fe929..e5f3aef95d 100644
--- a/io.c
+++ b/io.c
@@ -4629,21 +4629,36 @@ clear_codeconv(rb_io_t *fptr)
     clear_writeconv(fptr);
 }
 
-int
-rb_io_fptr_finalize(rb_io_t *fptr)
+void
+rb_io_fptr_finalize_internal(void *ptr)
 {
-    if (!fptr) return 0;
+    rb_io_t *fptr = ptr;
+
+    if (!ptr) return;
     fptr->pathv = Qnil;
     if (0 <= fptr->fd)
-	rb_io_fptr_cleanup(fptr, TRUE);
+        rb_io_fptr_cleanup(fptr, TRUE);
     fptr->write_lock = 0;
     free_io_buffer(&fptr->rbuf);
     free_io_buffer(&fptr->wbuf);
     clear_codeconv(fptr);
     free(fptr);
-    return 1;
 }
 
+#undef rb_io_fptr_finalize
+int
+rb_io_fptr_finalize(rb_io_t *fptr)
+{
+    if (!fptr) {
+        return 0;
+    }
+    else {
+        rb_io_fptr_finalize_internal(fptr);
+        return 1;
+    }
+}
+#define rb_io_fptr_finalize(fptr) rb_io_fptr_finalize_internal(fptr)
+
 RUBY_FUNC_EXPORTED size_t
 rb_io_memsize(const rb_io_t *fptr)
 {