diff --git a/win32/build/config.w32.h.in b/win32/build/config.w32.h.in
index d12599d77f2..a22c902ac0d 100644
--- a/win32/build/config.w32.h.in
+++ b/win32/build/config.w32.h.in
@@ -160,3 +160,4 @@
 #endif
 #define HAVE_STDLIB_H 1
 
+#define va_copy(ap1, ap2) memcpy(&ap1, &ap2, sizeof(va_list))