diff --git a/src/x11_window.c b/src/x11_window.c
index 271e1080..3c03ccda 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -2950,8 +2950,9 @@ void _glfwPlatformSetCursor(_GLFWwindow* window, _GLFWcursor* cursor)
 
 void _glfwPlatformSetClipboardString(const char* string)
 {
+    char* copy = _glfw_strdup(string);
     free(_glfw.x11.clipboardString);
-    _glfw.x11.clipboardString = _glfw_strdup(string);
+    _glfw.x11.clipboardString = copy;
 
     XSetSelectionOwner(_glfw.x11.display,
                        _glfw.x11.CLIPBOARD,