diff --git a/ext/io/console/extconf.rb b/ext/io/console/extconf.rb
index 8cb3c4ea4e..153643c898 100644
--- a/ext/io/console/extconf.rb
+++ b/ext/io/console/extconf.rb
@@ -5,7 +5,7 @@ hdr = nil
 case
 when macro_defined?("_WIN32", "")
   # rb_w32_map_errno: 1.8.7
-  vk_header = ($nmake == ?n ? "{$(srcdir)}" : "") << "win32_vk.chksum"
+  vk_header = ($nmake == ?m ? "{$(srcdir)}" : "") << "win32_vk.chksum"
 when hdr = %w"termios.h termio.h".find {|h| have_header(h)}
   have_func("cfmakeraw", hdr)
 when have_header(hdr = "sgtty.h")
@@ -14,7 +14,7 @@ else
   ok = false
 end
 if ok
-  have_header("sys/ioctl.h")
+  have_header("sys/ioctl.h") if hdr
   # rb_check_hash_type: 1.9.3
   # rb_io_get_write_io: 1.9.1
   # rb_cloexec_open: 2.0.0