diff --git a/include/SDL_syswm.h b/include/SDL_syswm.h
index fcb3a3563..762bf452a 100644
--- a/include/SDL_syswm.h
+++ b/include/SDL_syswm.h
@@ -280,8 +280,9 @@ struct SDL_SysWMinfo
         } vivante;
 #endif
 
-        /* Can't have an empty union */
-        int dummy;
+        /* Make sure this union is always 64 bytes (8 64-bit pointers). */
+        /* Be careful not to overflow this if you add a new target! */
+        Uint8 dummy[64];
     } info;
 };
 
diff --git a/src/video/directfb/SDL_DirectFB_window.c b/src/video/directfb/SDL_DirectFB_window.c
index a66aa5950..936e0a008 100644
--- a/src/video/directfb/SDL_DirectFB_window.c
+++ b/src/video/directfb/SDL_DirectFB_window.c
@@ -458,9 +458,28 @@ SDL_bool
 DirectFB_GetWindowWMInfo(_THIS, SDL_Window * window,
                          struct SDL_SysWMinfo * info)
 {
+    const Uint32 version = ((((Uint32) info->version.major) * 1000000) +
+                            (((Uint32) info->version.minor) * 10000) +
+                            (((Uint32) info->version.patch)));
+
     SDL_DFB_DEVICEDATA(_this);
     SDL_DFB_WINDOWDATA(window);
 
+    /* Before 2.0.6, it was possible to build an SDL with DirectFB support
+       (SDL_SysWMinfo will be large enough to hold DirectFB info), but build
+       your app against SDL headers that didn't have DirectFB support
+       (SDL_SysWMinfo could be smaller than Wayland needs. This would lead
+       to an app properly using SDL_GetWindowWMInfo() but we'd accidentally
+       overflow memory on the stack or heap. To protect against this, we've
+       padded out the struct unconditionally in the headers and DirectFB will
+       just return an error for older apps using this function. Those apps
+       will need to be recompiled against newer headers or not use DirectFB,
+       maybe by forcing SDL_VIDEODRIVER=x11. */
+    if (version < 2000006) {
+        info->subsystem = SDL_SYSWM_UNKNOWN;
+        return SDL_FALSE;
+    }
+
     if (info->version.major == SDL_MAJOR_VERSION &&
         info->version.minor == SDL_MINOR_VERSION) {
         info->subsystem = SDL_SYSWM_DIRECTFB;
diff --git a/src/video/wayland/SDL_waylandwindow.c b/src/video/wayland/SDL_waylandwindow.c
index db0fbe5f7..7113485f6 100644
--- a/src/video/wayland/SDL_waylandwindow.c
+++ b/src/video/wayland/SDL_waylandwindow.c
@@ -129,6 +129,24 @@ SDL_bool
 Wayland_GetWindowWMInfo(_THIS, SDL_Window * window, SDL_SysWMinfo * info)
 {
     SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
+    const Uint32 version = ((((Uint32) info->version.major) * 1000000) +
+                            (((Uint32) info->version.minor) * 10000) +
+                            (((Uint32) info->version.patch)));
+
+    /* Before 2.0.6, it was possible to build an SDL with Wayland support
+       (SDL_SysWMinfo will be large enough to hold Wayland info), but build
+       your app against SDL headers that didn't have Wayland support
+       (SDL_SysWMinfo could be smaller than Wayland needs. This would lead
+       to an app properly using SDL_GetWindowWMInfo() but we'd accidentally
+       overflow memory on the stack or heap. To protect against this, we've
+       padded out the struct unconditionally in the headers and Wayland will
+       just return an error for older apps using this function. Those apps
+       will need to be recompiled against newer headers or not use Wayland,
+       maybe by forcing SDL_VIDEODRIVER=x11. */
+    if (version < 2000006) {
+        info->subsystem = SDL_SYSWM_UNKNOWN;
+        return SDL_FALSE;
+    }
 
     info->info.wl.display = data->waylandData->display;
     info->info.wl.surface = data->surface;