diff --git a/desmume/src/frontend/posix/cli/main.cpp b/desmume/src/frontend/posix/cli/main.cpp
index acfc5a3e1..194245fe9 100644
--- a/desmume/src/frontend/posix/cli/main.cpp
+++ b/desmume/src/frontend/posix/cli/main.cpp
@@ -18,6 +18,7 @@
  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 02111-1307, USA.
  */
+#include <X11/Xlib.h>
 #include <SDL.h>
 #include <SDL_thread.h>
 #include <stdlib.h>
@@ -627,6 +628,12 @@ int main(int argc, char ** argv) {
 
   execute = true;
 
+  /* X11 multi-threading support */
+  if(!XInitThreads())
+    {
+      fprintf(stderr, "Warning: X11 not thread-safe\n");
+    }
+
   if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) == -1)
     {
       fprintf(stderr, "Error trying to initialize SDL: %s\n",
diff --git a/desmume/src/frontend/posix/cli/meson.build b/desmume/src/frontend/posix/cli/meson.build
index f33813d3f..d3eb234f1 100644
--- a/desmume/src/frontend/posix/cli/meson.build
+++ b/desmume/src/frontend/posix/cli/meson.build
@@ -1,3 +1,7 @@
+dep_x11 = dependency('x11')
+
+cli_dependencies = dependencies + [dep_x11]
+
 cli_src = [
   'main.cpp',
   '../shared/sndsdl.cpp',
@@ -13,7 +17,7 @@ includes = include_directories(
 
 executable('desmume-cli',
   cli_src,
-  dependencies: dependencies,
+  dependencies: cli_dependencies,
   include_directories: includes,
   link_with: libdesmume,
   install: true,
diff --git a/desmume/src/frontend/posix/gtk/main.cpp b/desmume/src/frontend/posix/gtk/main.cpp
index 3e31274d0..2ad7c43f7 100644
--- a/desmume/src/frontend/posix/gtk/main.cpp
+++ b/desmume/src/frontend/posix/gtk/main.cpp
@@ -29,6 +29,7 @@
 #include <gio/gapplication.h>
 #include <gdk/gdkkeysyms.h>
 #include <SDL.h>
+#include <X11/Xlib.h>
 #include <vector>
 
 #include "types.h"
@@ -4590,6 +4591,12 @@ int main (int argc, char *argv[])
   my_config.parse(argc, argv);
   init_configured_features( &my_config);
 
+  /* X11 multi-threading support */
+  if(!XInitThreads())
+    {
+      fprintf(stderr, "Warning: X11 not thread-safe\n");
+    }
+
   // TODO: pass G_APPLICATION_HANDLES_COMMAND_LINE instead.
   GtkApplication *app = gtk_application_new("org.desmume.DeSmuME", G_APPLICATION_HANDLES_OPEN);
   g_signal_connect (app, "activate", G_CALLBACK(common_gtk_main), &my_config);
diff --git a/desmume/src/frontend/posix/gtk/meson.build b/desmume/src/frontend/posix/gtk/meson.build
index caceaae39..20a31da12 100644
--- a/desmume/src/frontend/posix/gtk/meson.build
+++ b/desmume/src/frontend/posix/gtk/meson.build
@@ -1,6 +1,7 @@
 dep_gtk3 = dependency('gtk+-3.0', version: '>=3.24')
+dep_x11 = dependency('x11')
 
-gtk_dependencies = dependencies + [dep_gtk3]
+gtk_dependencies = dependencies + [dep_gtk3, dep_x11]
 
 desmume_src = [
   'avout_pipe_base.cpp',