diff --git a/src/video/x11/SDL_x11events.c b/src/video/x11/SDL_x11events.c
index b82590071e..979ce0ea04 100644
--- a/src/video/x11/SDL_x11events.c
+++ b/src/video/x11/SDL_x11events.c
@@ -1862,8 +1862,8 @@ static void X11_DispatchEvent(SDL_VideoDevice *_this, XEvent *xevent)
 
     case ButtonPress:
     {
-        if (data->xinput2_mouse_enabled) {
-            // This input is being handled by XInput2
+        if (data->xinput2_mouse_enabled && xevent->xbutton.serial == videodata->xinput_last_button_serial) {
+            // This input event was handled by XInput2.
             break;
         }
 
@@ -1873,8 +1873,8 @@ static void X11_DispatchEvent(SDL_VideoDevice *_this, XEvent *xevent)
 
     case ButtonRelease:
     {
-        if (data->xinput2_mouse_enabled) {
-            // This input is being handled by XInput2
+        if (data->xinput2_mouse_enabled && xevent->xbutton.serial == videodata->xinput_last_button_serial) {
+            // This input event was handled by XInput2.
             break;
         }
 
diff --git a/src/video/x11/SDL_x11video.h b/src/video/x11/SDL_x11video.h
index 2dc4d3ab60..c6069b2624 100644
--- a/src/video/x11/SDL_x11video.h
+++ b/src/video/x11/SDL_x11video.h
@@ -138,6 +138,7 @@ struct SDL_VideoData
     Uint32 global_mouse_buttons;
 
     SDL_XInput2DeviceInfo *mouse_device_info;
+    unsigned long xinput_last_button_serial;
     int xinput_master_pointer_device;
     bool xinput_hierarchy_changed;
 
diff --git a/src/video/x11/SDL_x11xinput2.c b/src/video/x11/SDL_x11xinput2.c
index 51a18a66e5..21c0f5b15d 100644
--- a/src/video/x11/SDL_x11xinput2.c
+++ b/src/video/x11/SDL_x11xinput2.c
@@ -607,8 +607,16 @@ void X11_HandleXinput2Event(SDL_VideoDevice *_this, XGenericEventCookie *cookie)
             SDL_WindowData *windowdata = X11_FindWindow(videodata, xev->event);
             int x_ticks = 0, y_ticks = 0;
 
-            // Slave pointer devices don't have button remapping applied automatically, so do it manually.
+            // Store the button serial to filter out redundant core button events.
+            videodata->xinput_last_button_serial = xev->serial;
+
             if (xev->deviceid != videodata->xinput_master_pointer_device) {
+                // Ignore slave button events on non-focused windows, or focus can be incorrectly set while a grab is active.
+                if (SDL_GetMouseFocus() != windowdata->window) {
+                    break;
+                }
+
+                // Slave pointer devices don't have button remapping applied automatically, so do it manually.
                 if (button <= xinput2_pointer_button_map_size) {
                     button = xinput2_pointer_button_map[button - 1];
                 }