diff --git a/lib/fusion.c b/lib/fusion.c
index 41e7bd3..b86205f 100644
--- a/lib/fusion.c
+++ b/lib/fusion.c
@@ -984,8 +984,7 @@
                                                sizeof(struct aesgcm_context),
                                                aes256gcm_setup};
 
-/* #ifdef _WINDOWS */
-#if 1
+#ifdef _WINDOWS
 /**
  * ptls_fusion_is_supported_by_cpu:
  * Check that the CPU has extended instructions for PCMUL, AES and AVX2.