diff --git a/common/xutil.c b/common/xutil.c
index a280f333..164d2c4c 100644
--- a/common/xutil.c
+++ b/common/xutil.c
@@ -115,6 +115,29 @@ xutil_key_mask_fromstr(const char *keyname, size_t len)
     }
 }
 
+void
+xutil_key_mask_tostr(uint16_t mask, const char **name, size_t *len)
+{
+    switch(mask)
+    {
+#define SET_RESULT(res) \
+        *name = #res; \
+        *len = sizeof(#res) - 1; \
+        return;
+      case XCB_MOD_MASK_SHIFT:   SET_RESULT(Shift)
+      case XCB_MOD_MASK_LOCK:    SET_RESULT(Lock)
+      case XCB_MOD_MASK_CONTROL: SET_RESULT(Control)
+      case XCB_MOD_MASK_1:       SET_RESULT(Mod1)
+      case XCB_MOD_MASK_2:       SET_RESULT(Mod2)
+      case XCB_MOD_MASK_3:       SET_RESULT(Mod3)
+      case XCB_MOD_MASK_4:       SET_RESULT(Mod4)
+      case XCB_MOD_MASK_5:       SET_RESULT(Mod5)
+      case XCB_BUTTON_MASK_ANY:  SET_RESULT(Any)
+      default:                   SET_RESULT(Unknown)
+#undef SET_RESULT
+    }
+}
+
 /** Permit to use mouse with many more buttons */
 #ifndef XCB_BUTTON_INDEX_6
 #define XCB_BUTTON_INDEX_6 6
diff --git a/common/xutil.h b/common/xutil.h
index 494383bb..8c26020c 100644
--- a/common/xutil.h
+++ b/common/xutil.h
@@ -36,6 +36,7 @@ void xutil_error_handler_catch_all_set(xcb_event_handlers_t *,
                                        xcb_generic_error_handler_t, void *);
 
 uint16_t xutil_key_mask_fromstr(const char *, size_t);
+void xutil_key_mask_tostr(uint16_t, const char **, size_t *);
 uint8_t xutil_button_fromint(int);
 
 /* Get the informations about the screen.