diff --git a/config.h.win32 b/config.h.win32
index 84995abce9..e8ff4cf2f7 100644
--- a/config.h.win32
+++ b/config.h.win32
@@ -86,6 +86,9 @@
  */
 #define WS_MSVC_NORETURN	__declspec(noreturn)
 
+/* Define if you have the floorl function. */
+#define HAVE_FLOORL 1
+
 /* Define if you have the gethostbyname2 function.  */
 /* #undef HAVE_GETHOSTBYNAME2 */