diff --git a/lib/socks.c b/lib/socks.c
index 9fc5b7948..edf9c5553 100644
--- a/lib/socks.c
+++ b/lib/socks.c
@@ -23,7 +23,7 @@
 
 #include "setup.h"
 
-#ifndef CURL_DISABLE_PROXY
+#if !defined(CURL_DISABLE_PROXY) || defined(USE_WINDOWS_SSPI)
 #include <string.h>
 
 #ifdef NEED_MALLOC_H