diff --git a/src/xfns.c b/src/xfns.c
index bfb61c1205e..baa643bde07 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -2402,7 +2402,7 @@ append_wm_protocols (struct x_display_info *dpyinfo,
   if (!found_wm_ping)
     protos[num_protos++] = dpyinfo->Xatom_net_wm_ping;
 #if !defined HAVE_GTK3 && defined HAVE_XSYNC
-  if (!found_wm_sync_request)
+  if (!found_wm_sync_request && dpyinfo->xsync_supported_p)
     protos[num_protos++] = dpyinfo->Xatom_net_wm_sync_request;
 #endif
 
diff --git a/src/xterm.c b/src/xterm.c
index 4b4eae53be5..0d0a08d078b 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -9103,7 +9103,8 @@ handle_one_xevent (struct x_display_info *dpyinfo,
 
 #if defined HAVE_XSYNC && !defined HAVE_GTK3
 	    if (event->xclient.data.l[0] == dpyinfo->Xatom_net_wm_sync_request
-		&& event->xclient.format == 32)
+		&& event->xclient.format == 32
+		&& dpyinfo->xsync_supported_p)
 	      {
 		struct frame *f
 		  = x_top_window_to_frame (dpyinfo,
@@ -14784,7 +14785,7 @@ x_free_frame_resources (struct frame *f)
 #endif /* !USE_X_TOOLKIT */
 
 #ifdef HAVE_XSYNC
-      if (FRAME_X_BASIC_COUNTER (f))
+      if (FRAME_X_BASIC_COUNTER (f) != None)
 	XSyncDestroyCounter (FRAME_X_DISPLAY (f),
 			     FRAME_X_BASIC_COUNTER (f));
 #endif