diff --git a/win32/build/config.w32.h.in b/win32/build/config.w32.h.in
index a1729cd479c..8b8aab28be7 100644
--- a/win32/build/config.w32.h.in
+++ b/win32/build/config.w32.h.in
@@ -148,6 +148,7 @@
 
 /* Win32 supports socketpair by the emulation in win32/sockets.c */
 #define HAVE_SOCKETPAIR 1
+#define HAVE_SOCKLEN_T 1
 
 /* Win32 support proc_open */
 #define PHP_CAN_SUPPORT_PROC_OPEN 1