diff --git a/srcs/juloo.keyboard2/Config.java b/srcs/juloo.keyboard2/Config.java
index b38604b..53bd2d2 100644
--- a/srcs/juloo.keyboard2/Config.java
+++ b/srcs/juloo.keyboard2/Config.java
@@ -185,7 +185,14 @@ final class Config
     final Set<KeyValue> extra_keys = new HashSet<KeyValue>();
     final Set<KeyValue> remove_keys = new HashSet<KeyValue>();
     if (extra_keys_subtype != null)
-      extra_keys_subtype.compute(extra_keys, kw.script);
+    {
+      Set<KeyValue> present = new HashSet<KeyValue>();
+      kw.getKeys(present);
+      present.addAll(extra_keys_param);
+      present.addAll(extra_keys_custom);
+      extra_keys_subtype.compute(extra_keys,
+          new ExtraKeys.Query(kw.script, present));
+    }
     extra_keys.addAll(extra_keys_param);
     extra_keys.addAll(extra_keys_custom);
     boolean number_row = this.number_row && !show_numpad;
diff --git a/srcs/juloo.keyboard2/ExtraKeys.java b/srcs/juloo.keyboard2/ExtraKeys.java
index 22187c1..36acaf1 100644
--- a/srcs/juloo.keyboard2/ExtraKeys.java
+++ b/srcs/juloo.keyboard2/ExtraKeys.java
@@ -1,6 +1,7 @@
 package juloo.keyboard2;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -8,50 +9,86 @@ import java.util.Set;
 
 class ExtraKeys
 {
-  Map<String, List<KeyValue>> _keys_per_script;
+  List<ExtraKey> _ks;
 
   public ExtraKeys()
   {
-    _keys_per_script = new HashMap<String, List<KeyValue>>();
+    _ks = new ArrayList<ExtraKey>();
   }
 
-  public void add_keys_for_script(String script, List<KeyValue> kvs)
+  public void parse_and_add_keys_for_script(String script, String extra_keys_str)
   {
-    List<KeyValue> ks = _keys_per_script.get(script);
-    if (ks == null) ks = new ArrayList<KeyValue>();
-    ks.addAll(kvs);
-    _keys_per_script.put(script, ks);
+    _ks.addAll(parse_extra_keys(script, extra_keys_str));
   }
 
-  /** Add the keys that should be added to the keyboard into [dst]. [null] is
-      a valid script. */
-  public void compute(Set<KeyValue> dst, String script)
+  /** Add the keys that should be added to the keyboard into [dst]. */
+  public void compute(Set<KeyValue> dst, Query q)
   {
-    if (script == null)
+    for (ExtraKey k : _ks)
     {
-      for (String sc : _keys_per_script.keySet())
-        get_keys_of_script(dst, sc);
-    }
-    else
-    {
-      get_keys_of_script(dst, null);
-      get_keys_of_script(dst, script);
+      if (k.should_add(q))
+        dst.add(k.kv);
     }
   }
 
-  void get_keys_of_script(Set<KeyValue> dst, String script)
+  public static List<ExtraKey> parse_extra_keys(String script, String str)
   {
-    List<KeyValue> ks = _keys_per_script.get(script);
-    if (ks != null)
-      dst.addAll(ks);
-  }
-
-  public static List<KeyValue> parse_extra_keys(String str)
-  {
-    List<KeyValue> dst = new ArrayList<KeyValue>();
+    List<ExtraKey> dst = new ArrayList<ExtraKey>();
     String[] ks = str.split("\\|");
     for (int i = 0; i < ks.length; i++)
-      dst.add(KeyValue.getKeyByName(ks[i]));
+      dst.add(ExtraKey.parse(ks[i], script));
     return dst;
   }
+
+  final static class ExtraKey
+  {
+    /** The key to add. */
+    final KeyValue kv;
+    /** The key will be added to layouts of the same script. If null, might be
+        added to layouts of any script. */
+    final String script;
+    /** The key will not be added to layout that already contain all the
+        alternatives. */
+    final List<KeyValue> alternatives;
+
+    ExtraKey(KeyValue kv_, String script_, List<KeyValue> alts_)
+    {
+      kv = kv_;
+      script = script_;
+      alternatives = alts_;
+    }
+
+    /** Whether the key should be added to the keyboard. */
+    public boolean should_add(Query q)
+    {
+      return
+        (q.script == null || script == null || q.script.equals(script))
+        && (alternatives.size() == 0 || !q.present.containsAll(alternatives));
+    }
+
+    /** Extra keys are of the form "key name" or "key name:alt 1:alt 2". */
+    public static ExtraKey parse(String str, String script)
+    {
+      String[] strs = str.split(":");
+      KeyValue kv = KeyValue.getKeyByName(strs[0]);
+      KeyValue[] alts = new KeyValue[strs.length-1];
+      for (int i = 1; i < strs.length; i++)
+        alts[i-1] = KeyValue.getKeyByName(strs[i]);
+      return new ExtraKey(kv, script, Arrays.asList(alts));
+    }
+  }
+
+  public final static class Query
+  {
+    /** Script of the current layout. Might be null. */
+    final String script;
+    /** Keys present on the layout. */
+    final Set<KeyValue> present;
+
+    public Query(String script_, Set<KeyValue> present_)
+    {
+      script = script_;
+      present = present_;
+    }
+  }
 }
diff --git a/srcs/juloo.keyboard2/Keyboard2.java b/srcs/juloo.keyboard2/Keyboard2.java
index 1b59e5e..77c2c15 100644
--- a/srcs/juloo.keyboard2/Keyboard2.java
+++ b/srcs/juloo.keyboard2/Keyboard2.java
@@ -114,9 +114,8 @@ public class Keyboard2 extends InputMethodService
   {
     String extra_keys = subtype.getExtraValueOf("extra_keys");
     String script = subtype.getExtraValueOf("script");
-    if (extra_keys == null)
-      return;
-    dst.add_keys_for_script(script, ExtraKeys.parse_extra_keys(extra_keys));
+    if (extra_keys != null)
+      dst.parse_and_add_keys_for_script(script, extra_keys);
   }
 
   private void refreshAccentsOption(InputMethodManager imm, InputMethodSubtype subtype)