diff --git a/src/gui/gui-key.c b/src/gui/gui-key.c
index 429421e97..911e86b5b 100644
--- a/src/gui/gui-key.c
+++ b/src/gui/gui-key.c
@@ -1236,6 +1236,125 @@ gui_key_is_safe (int context, const char *key)
     return 0;
 }
 
+/*
+ * Checks if the key chunk seems valid.
+ *
+ * Example of valid key chunk:
+ *   "meta-a"
+ *   "meta-c"
+ *   "meta-up"
+ *   "ctrl-left"
+ *   "ctrl-u"
+ *
+ * Example of raw codes or invalid keys:
+ *   "meta-[A"  (raw code)
+ *   "ctrl-cb"  (invalid: missing comma)
+ *
+ * Returns:
+ *   1: key chunk seems valid
+ *   0: key chunk seems either invalid or a raw code
+ */
+
+int
+gui_key_chunk_seems_valid (const char *chunk)
+{
+    int i, found, length;
+
+    if (!chunk || !chunk[0])
+        return 0;
+
+    /* skip modifiers */
+    found = 1;
+    while (found)
+    {
+        found = 0;
+        for (i = 0; gui_key_modifier_list[i]; i++)
+        {
+            length = strlen (gui_key_modifier_list[i]);
+            if (strncmp (chunk, gui_key_modifier_list[i], length) == 0)
+            {
+                chunk += length;
+                found = 1;
+                break;
+            }
+        }
+    }
+
+    /* check if it's an alias */
+    found = 0;
+    for (i = 0; gui_key_alias_list[i]; i++)
+    {
+        length = strlen (gui_key_alias_list[i]);
+        if (strncmp (chunk, gui_key_alias_list[i], length) == 0)
+        {
+            chunk += length;
+            found = 1;
+            break;
+        }
+    }
+    if (!found)
+        chunk = utf8_next_char (chunk);
+
+    if (chunk[0])
+        return 0;
+
+    return 1;
+}
+
+/*
+ * Checks if the key seems valid: not a raw code, and no comma is missing.
+ *
+ * Example of valid keys:
+ *   "meta-a"
+ *   "meta-c,b"
+ *   "meta-w,meta-up"
+ *   "ctrl-left"
+ *   "ctrl-u"
+ *
+ * Example of raw codes or invalid keys:
+ *   "meta-[A"  (raw code)
+ *   "ctrl-cb"  (invalid: missing comma)
+ *
+ * Returns:
+ *   1: key seems valid
+ *   0: key seems either invalid or a raw code
+ */
+
+int
+gui_key_seems_valid (int context, const char *key)
+{
+    char **chunks;
+    int i, rc, chunks_count;
+
+    if (!key || !key[0])
+        return 0;
+
+    /* "@" is allowed at beginning for cursor/mouse contexts */
+    if ((key[0] == '@')
+        && ((context == GUI_KEY_CONTEXT_CURSOR)
+            || (context == GUI_KEY_CONTEXT_MOUSE)))
+    {
+        return 1;
+    }
+
+    chunks = string_split (key, ",", NULL, 0, 0, &chunks_count);
+    if (!chunks)
+        return 0;
+
+    rc = 1;
+    for (i = 0; i < chunks_count; i++)
+    {
+        if (!gui_key_chunk_seems_valid (chunks[i]))
+        {
+            rc = 0;
+            break;
+        }
+    }
+
+    string_free_split (chunks);
+    return rc;
+}
+
 /*
  * Callback for changes on a key option.
  */
@@ -1575,6 +1694,15 @@ gui_key_bind (struct t_gui_buffer *buffer, int context, const char *key,
             }
             return NULL;
         }
+        if (!gui_key_seems_valid (context, key))
+        {
+            gui_chat_printf (
+                NULL,
+                _("%sWarning: key \"%s\" seems either a raw code or invalid, "
+                  "it may not work (see /help key)"),
+                gui_chat_prefix[GUI_CHAT_PREFIX_ERROR],
+                key);
+        }
     }
 
     gui_key_unbind (buffer, context, key);
diff --git a/tests/unit/gui/test-gui-key.cpp b/tests/unit/gui/test-gui-key.cpp
index f81cfd47d..5596279a4 100644
--- a/tests/unit/gui/test-gui-key.cpp
+++ b/tests/unit/gui/test-gui-key.cpp
@@ -35,6 +35,7 @@ extern int gui_key_get_current_context ();
 extern char *gui_key_legacy_internal_code (const char *key);
 extern char *gui_key_fix (const char *key);
 extern int gui_key_is_safe (int context, const char *key);
+extern int gui_key_seems_valid (int context, const char *key);
 extern struct t_config_option *gui_key_new_option (int context,
                                                    const char *name,
                                                    const char *value);
@@ -1034,6 +1035,44 @@ TEST(GuiKey, IsSafe)
     LONGS_EQUAL(1, gui_key_is_safe (GUI_KEY_CONTEXT_MOUSE, "@"));
 }
 
+/*
+ * Tests functions:
+ *   gui_key_chunk_seems_valid
+ *   gui_key_seems_valid
+ */
+
+TEST(GuiKey, SeemsValid)
+{
+    /* invalid: NULL or empty string */
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, NULL));
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, ""));
+
+    /* raw codes: considered not valid */
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-[A"));
+
+    /* invalid keys: missing comma */
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "ab"));
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "@a"));
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "homeZ"));
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-cb"));
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-updown"));
+    LONGS_EQUAL(0, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "@chat:button1"));
+
+    /* valid keys */
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "a"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "A"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "é"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "/"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-a"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-ctrl-a"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-c,b"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "meta-w,meta-up"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "ctrl-left"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_DEFAULT, "ctrl-u"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_CURSOR, "@chat:q"));
+    LONGS_EQUAL(1, gui_key_seems_valid (GUI_KEY_CONTEXT_MOUSE, "@chat:button1"));
+}
+
 /*
  * Tests functions:
  *   gui_key_option_change_cb