diff --git a/shell/browser/ui/x/x_window_utils.cc b/shell/browser/ui/x/x_window_utils.cc
index 7289f23b2dba..fd0c5ec3aa30 100644
--- a/shell/browser/ui/x/x_window_utils.cc
+++ b/shell/browser/ui/x/x_window_utils.cc
@@ -19,13 +19,6 @@
 
 namespace electron {
 
-void SetWMSpecState(x11::Window window, bool enabled, x11::Atom state) {
-  ui::SendClientMessage(
-      window, ui::GetX11RootWindow(), x11::GetAtom("_NET_WM_STATE"),
-      {static_cast<uint32_t>(enabled ? 1 : 0), static_cast<uint32_t>(state),
-       static_cast<uint32_t>(x11::Window::None), 1, 0});
-}
-
 void SetWindowType(x11::Window window, const std::string& type) {
   std::string type_prefix = "_NET_WM_WINDOW_TYPE_";
   std::string window_type_str = type_prefix + base::ToUpperASCII(type);
diff --git a/shell/browser/ui/x/x_window_utils.h b/shell/browser/ui/x/x_window_utils.h
index 0d909f25d64b..767eb2112b4a 100644
--- a/shell/browser/ui/x/x_window_utils.h
+++ b/shell/browser/ui/x/x_window_utils.h
@@ -11,10 +11,6 @@
 
 namespace electron {
 
-// Sends a message to the x11 window manager, enabling or disabling the |state|
-// for _NET_WM_STATE.
-void SetWMSpecState(x11::Window window, bool enabled, x11::Atom state);
-
 // Sets the _NET_WM_WINDOW_TYPE of window.
 void SetWindowType(x11::Window window, const std::string& type);