diff --git a/include/os.h b/include/os.h
index 675d5335d..50bd4fa2d 100644
--- a/include/os.h
+++ b/include/os.h
@@ -194,17 +194,6 @@ PrivsElevated(void);
 extern _X_EXPORT int
 GetClientFd(ClientPtr);
 
-/* stuff for ReplyCallback */
-extern _X_EXPORT CallbackListPtr ReplyCallback;
-typedef struct {
-    ClientPtr client;
-    const void *replyData;
-    unsigned long dataLenBytes; /* actual bytes from replyData + pad bytes */
-    unsigned long bytesRemaining;
-    Bool startOfReply;
-    unsigned long padBytes;     /* pad bytes from zeroed array */
-} ReplyInfoRec;
-
 /* stuff for FlushCallback */
 extern _X_EXPORT CallbackListPtr FlushCallback;
 
diff --git a/os/client_priv.h b/os/client_priv.h
index d0642f131..4cfa98f8d 100644
--- a/os/client_priv.h
+++ b/os/client_priv.h
@@ -10,6 +10,8 @@
 #include <X11/Xdefs.h>
 #include <X11/Xfuncproto.h>
 
+#include "include/callback.h"
+
 /* Client IDs. Use GetClientPid, GetClientCmdName and GetClientCmdArgs
  * instead of accessing the fields directly. */
 struct _ClientId {
@@ -60,4 +62,15 @@ _X_EXPORT void SetCriticalOutputPending(void);
 /* exported only for DRI module, but should not be used by external drivers */
 _X_EXPORT void ResetCurrentRequest(struct _Client *client);
 
+/* stuff for ReplyCallback */
+extern CallbackListPtr ReplyCallback;
+typedef struct {
+    ClientPtr client;
+    const void *replyData;
+    unsigned long dataLenBytes; /* actual bytes from replyData + pad bytes */
+    unsigned long bytesRemaining;
+    Bool startOfReply;
+    unsigned long padBytes;     /* pad bytes from zeroed array */
+} ReplyInfoRec;
+
 #endif /* _XSERVER_DIX_CLIENT_PRIV_H */
diff --git a/os/io.c b/os/io.c
index 9c53cc7e6..8c5d60e29 100644
--- a/os/io.c
+++ b/os/io.c
@@ -82,7 +82,7 @@ SOFTWARE.
 #include "dixstruct.h"
 #include "misc.h"
 
-CallbackListPtr ReplyCallback;
+CallbackListPtr ReplyCallback = NULL;
 CallbackListPtr FlushCallback;
 
 typedef struct _connectionInput {