diff --git a/lib/urldata.h b/lib/urldata.h
index 79d4ffe25..9b3fcf7dd 100644
--- a/lib/urldata.h
+++ b/lib/urldata.h
@@ -193,7 +193,7 @@ typedef enum {
  * or SECURITY_KERNEL, indicating who is compiling the code.
  */
 #define SECURITY_WIN32 1
-#include <Security.h>
+#include <security.h>
 #include <sspi.h>
 #include <rpc.h>
 #endif