diff --git a/glib/glibconfig.h.win32.in b/glib/glibconfig.h.win32.in
index 13b2e6975..637ccf4f9 100644
--- a/glib/glibconfig.h.win32.in
+++ b/glib/glibconfig.h.win32.in
@@ -206,7 +206,7 @@ typedef unsigned __int64 guintptr;
 
 #define G_THREADS_ENABLED
 #define G_THREADS_IMPL_WIN32
-typedef struct _GMutex* GStaticMutex;
+typedef union _GMutex* GStaticMutex;
 #define G_STATIC_MUTEX_INIT NULL
 /* This represents a system thread as used by the implementation. An
  * alien implementaion, as loaded by g_thread_init can only count on