diff --git a/source/textbox.c b/source/textbox.c
index 8aa6b250..6e1679a5 100644
--- a/source/textbox.c
+++ b/source/textbox.c
@@ -45,6 +45,7 @@
 // Use this so we can ignore numlock mask.
 // TODO: maybe use something smarter here..
 extern unsigned int NumlockMask;
+extern unsigned int ModeSwitchMask;
 
 /**
  * Font + font color cache.
@@ -574,7 +575,7 @@ int textbox_keypress ( textbox *tb, XIC xic, XEvent *ev )
     }
     // Filter When alt/ctrl/etc is pressed do not accept the character.
     // Ignore others (numlock, shift,..).
-    else if ( !iscntrl ( *pad ) && 0 == ( ev->xkey.state & ~( NumlockMask | ( 1 << 12 ) | ( 1 << 13 ) | ShiftMask | LockMask ) ) ) {
+    else if ( !iscntrl ( *pad ) && 0 == ( ev->xkey.state & ~( ModeSwitchMask | NumlockMask | ( 1 << 12 ) | ( 1 << 13 ) | ShiftMask | LockMask ) ) ) {
         textbox_insert ( tb, tb->cursor, pad );
         textbox_cursor_inc ( tb );
         return 1;
diff --git a/source/x11-helper.c b/source/x11-helper.c
index a602c9a5..cda8c674 100644
--- a/source/x11-helper.c
+++ b/source/x11-helper.c
@@ -58,6 +58,7 @@ Atom            netatoms[NUM_NETATOMS];
 const char      *netatom_names[] = { EWMH_ATOMS ( ATOM_CHAR ) };
 // Mask indicating num-lock.
 unsigned int    NumlockMask = 0;
+unsigned int   ModeSwitchMask = 0;
 
 extern Colormap map;
 
@@ -369,11 +370,15 @@ static void x11_figure_out_numlock_mask ( Display *display )
 {
     XModifierKeymap *modmap = XGetModifierMapping ( display );
     KeyCode         kc      = XKeysymToKeycode ( display, XK_Num_Lock );
+    KeyCode         kc_ms   = XKeysymToKeycode ( display, XK_Mode_switch);
     for ( int i = 0; i < 8; i++ ) {
         for ( int j = 0; j < ( int ) modmap->max_keypermod; j++ ) {
             if ( modmap->modifiermap[i * modmap->max_keypermod + j] == kc ) {
                 NumlockMask = ( 1 << i );
             }
+            if ( modmap->modifiermap[i * modmap->max_keypermod + j] == kc_ms ) {
+                ModeSwitchMask = ( 1 << i );
+            }
         }
     }
     XFreeModifiermap ( modmap );