diff --git a/src/86box.c b/src/86box.c
index cf992df4c..0f72ddef1 100644
--- a/src/86box.c
+++ b/src/86box.c
@@ -1870,6 +1870,27 @@ update_mouse_msg(void)
              (mouse_get_buttons() > 2) ? plat_get_string(STRING_MOUSE_RELEASE) : plat_get_string(STRING_MOUSE_RELEASE_MMB));
     swprintf(mouse_msg[2], sizeof_w(mouse_msg[2]), L"%ls v%ls - %%i%%%% - %ls - %ls/%ls",
              EMU_NAME_W, EMU_VERSION_FULL_W, wmachine, wcpufamily, wcpu);
+#else
+#ifdef __APPLE__
+    /*
+     * On macOS, BSD swprintf fails (returns -1) when the format string
+     * or a %ls argument contains non-ASCII wide characters (e.g. the
+     * native key symbols ⌘ U+2318, ⌫ U+232B) and the C locale is
+     * active.  Store just the message suffixes here; the title update
+     * path in pc_render_monitor_dispatch() builds the full string
+     * without swprintf.
+     */
+    wcsncpy(mouse_msg[0], plat_get_string(STRING_MOUSE_CAPTURE), sizeof_w(mouse_msg[0]) - 1);
+    mouse_msg[0][sizeof_w(mouse_msg[0]) - 1] = L'\0';
+
+    {
+        wchar_t *rel = (mouse_get_buttons() > 2) ? plat_get_string(STRING_MOUSE_RELEASE)
+                                                  : plat_get_string(STRING_MOUSE_RELEASE_MMB);
+        wcsncpy(mouse_msg[1], rel, sizeof_w(mouse_msg[1]) - 1);
+        mouse_msg[1][sizeof_w(mouse_msg[1]) - 1] = L'\0';
+    }
+
+    mouse_msg[2][0] = L'\0';
 #else
     swprintf(mouse_msg[0], sizeof_w(mouse_msg[0]), L"%%i%%%% - %ls",
              plat_get_string(STRING_MOUSE_CAPTURE));
@@ -1877,6 +1898,7 @@ update_mouse_msg(void)
              (mouse_get_buttons() > 2) ? plat_get_string(STRING_MOUSE_RELEASE) : plat_get_string(STRING_MOUSE_RELEASE_MMB));
     wcsncpy(mouse_msg[2], L"%i%%", sizeof_w(mouse_msg[2]));
 #endif
+#endif
 }
 
 void
@@ -2009,11 +2031,20 @@ pc_run(void)
         else
             fps = ((fps + 20) / 50) * 50;
 #endif
-        swprintf(temp, sizeof_w(temp), mouse_msg[mouse_msg_idx], fps / (force_10ms ? 1 : 10));
 #ifdef __APPLE__
+        /*
+         * mouse_msg[] stores suffixes only on macOS (see update_mouse_msg).
+         * Build the title without passing non-ASCII chars through swprintf.
+         */
+        swprintf(temp, sizeof_w(temp), L"%i%%", fps / (force_10ms ? 1 : 10));
+        if (mouse_msg[mouse_msg_idx][0]) {
+            wcsncat(temp, L" - ", sizeof_w(temp) - wcslen(temp) - 1);
+            wcsncat(temp, mouse_msg[mouse_msg_idx], sizeof_w(temp) - wcslen(temp) - 1);
+        }
         /* Needed due to modifying the UI on the non-main thread is a big no-no. */
         dispatch_async_f(dispatch_get_main_queue(), wcsdup((const wchar_t *) temp), _ui_window_title);
 #else
+        swprintf(temp, sizeof_w(temp), mouse_msg[mouse_msg_idx], fps / (force_10ms ? 1 : 10));
         ui_window_title(temp);
 #endif
         title_update = 0;